Musicians prohibited on radio (4)
I believe the answer is:
band
'musicians' is the definition.
(I've seen this before)
'prohibited on radio' is the wordplay.
'prohibited' becomes 'banned' (banning is a kind of prohibiting).
'on radio' indicates a 'sounds like' (homophone) clue.
'banned' is a homophone of 'BAND'.
(Other definitions for band that I've seen before include "troop" , "Outline drawing" , "Pop group; stripe" , "Zone; group" , "Musicians - circle" .)