Working Online for Clients outside of the UK

On securing a Tier 2 Employer sponsored visa after university, is it possible to work online via distance for existing or new clients? Eg Can a media content producer continue to approach clients worldwide, mainly the USA, to produce pop music or film composition or other media products if the income is not dependent on location and you are not competing with other UK content producers for jobs within the UK.

Also, is it legal or illegal to continue to make videos for an existing youtube channel as a solo musician/composer and be paid as a youtube partner while on a T2 visa? Would those be considered "produced in the UK" and, therefore, illegal?

Finally, what is the approved definition for an entertainer according to the Home Office? I can't seem to find the document with it. Is a sound engineer or sound tech considered an entertainer? What about camera crew or any other behind the scenes roles.

Thanks for the help.