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