Group of musicians prohibited on the radio (4)
I believe the answer is:
band
'group of musicians' is the definition.
(I've seen this before)
'prohibited on the radio' is the wordplay.
'prohibited' becomes 'banned' (banning is a kind of prohibiting).
'on the radio' indicates a 'sounds like' (homophone) clue.
'banned' sounds like 'BAND'.
(Other definitions for band that I've seen before include "Body" , "Belt; group of musicians" , "A collection of musicians in ring" , "Zone; group" , "Strip, belt; playing group" .)