It is a term that is widely used but hardly defined. What are the elements of an independent media?
To me, an independent media is a media that's only accountable to its readers. It is:
- Free of government control or reprisal. That is, its staff doesn't risk jail or harassment for writing about those exercising power.
- Free of corporate control or reprisal. That is, the media's owner is not firing or harassing staff when it's disgruntled by what they wrote or aired, and third parties cannot coerce it into not writing or airing things by e.g. stripping it of advertisement revenue or suing it out of existence.
Truly independent media outlets are few in practice. An example is the Canard Enchainé in France: it's a print-only satirical weekly that regularly breaks scandals in France. It's mostly owned by employees, accepts no ads or corporate sponsors, is profitable in spite of that, and has large cash reserves (over €100M) to weather the incessant stream of lawsuits that target them.
There are two definitions:
Definition one: media that is independent of formal larger powerful organizations.
This is largely covered in @denis's answer, and is the definition used in Wikipedia.
However, that definition is slightly mis-leading, in that, it implies that if the media outlet is independent of larger powerful organizations, then it somehow must be fully truly independent of external pressure.
Unfortunately, that's NOT the case:
First of all, people running the medial organization can be pressured by larger powerful organizations by means other than ownership (legal pressure, regulatory pressure, financial pressure, political pressure can all be applied - up to and including Charlie Hebdo level of pressure where you threaten to - or do - physically attack the journalists).
Media is dependent on not being sued out of existence.
Much as I personally delighted in Gawker's downfall, the larger point is worrysome - if you tick off someone powerful enough they may be able to sue you out of existence in best case, or simply influence your content by a threat of lawsuit.
Media is dependent on regulatory pressure regarding the media it uses.
When Democrats were in power in USA in early 21st century; there were calls to use regulatory FCC pressure to take down right wing radio stations (or force them to include left wing reporting).
Even Internet isn't a savior here - in many countries (including sometimes USA) there's large drive to regulate Internet content. In some countries like Russia or China it's largely fully under control already.
Yes, you may not directly depend on Big Something to pay your salary/budget. But what are you going to do when the financial or payments platform bans you because they don't like your content? Lauren Southern (conservative media person) had their account deleted by Patreon recently. Youtube demonetization explicitly targeted content disagreeable to people for political reasons. Stepping away from politics, TVTropes had to delete all sexual-related articles because Google refused to advertise there over the content. These are all real life examples that happened.
Now, imagine if US government pressures Mastercard and banks not to work with your media outlet, as they already easily do in case of sanctions or terrorism. Your media outlet is effectively done.
Threat of violence
Most media outlets self-censor many things that would get them in cross-hairs of violent extremists. Nobody wants to be a second Charlie Hebdo
Second, people can be pressured not by the large organization, but socially by groups of people.
If you're leaning left - like most journalists - it's very hard to be truly independent, since the moment you deviate in your content from the politically orthodox progressive view, you lose friends, you get called bad names, you get shunned. David Rubin covered this in some detail on several episodes of his podcast.
You don't have to be left wing in Western world for this effect. Imagine if you're a media outlet in Middle East critical of local tribal political issues. Local family heads would refuse to marry their daughters to you. Being a social pariah can have debilitating effects, especially in more tightly socially knit societies.
If you depend on subscriber payments, you are under pressure to not lose subscribers by publishing content that pushes them away. Sam Harris's podcast ran into this, he openly admitted that when he started relentlessly attacking Trump last couple of months, he lost many subscribers and paying supporters. That pressure didn't affect his content, but it IS big pressure and very well may affect other amedia outlet.
As such, truly fully independent media is nearly impossible to have. Only media less dependent on specific types of influence from specific interests.
Hot topic, indeed. Usually, the code of conduct is defined in the boundaries of each country (nationally). At least, theoretically, since in most cases journalists in practice are greatly affected by a) socio-economically powerful groups and b) by the media owner(s) himself, who has his own economical interests.
As for the individual journalist, surely, there cannot be a truly objective person (if that's what you imply by independent), since he is human and humans are subjective by nature, but the general idea is to 1) FIRST: present the news in a solid manner-facts only and afterwards 2) insert personal comment on the facts.
Some indicators which can be easily measured: 1) equality in distribution time of people/groups with opposite opinions (for example political parties), 2) avoidance of discrimination of religion, race, sexual-orientation, 3) public control of funding and relations of media owners
There are also some generic international frameworks, but not sure if they cover your question.
Respect for truth and for the right of the public to truth is the first duty of the journalist
In pursuance of this duty, the journalist shall at all times defend the principles of freedom in the honest collection and publication of news, and of the right of fair comment and criticism
The journalist shall report only in accordance with facts of which he/she knows the origin. The journalist shall not suppress essential information or falsify documents.
The journalist shall use only fair methods to obtain news, photographs and documents.
The journalist shall do the utmost to rectify any published information which is found to be harmfully inaccurate.
The journalist shall observe professional secrecy regarding the source of information obtained in confidence.
The journalist shall be aware of the danger of discrimination being furthered by the media, and shall do the utmost to avoid facilitating such discrimination based on, among other things, race, sex, sexual orientation, language, religion, political or other opinions, and national or social origins.
The journalist shall regard as grave professional offences the following:
calumny, slander, libel, unfounded accusations;
acceptance of a bribe in any form in consideration of either publication or suppression.
Journalists worthy of the name shall deem it their duty to observe faithfully the principles stated above. Within the general law of each country the journalist shall recognize in professional matters the jurisdiction of colleagues only, to the exclusion of every kind of interference by governments or others.