Unauthorised musicians on the radio (6)
I believe the answer is:
banned
'unauthorised' is the definition.
(thesaurus)
'musicians on the radio' is the wordplay.
'musicians' becomes 'band' (I've seen this before).
'on the radio' shows a homophone (sound like).
'band' is a homophone of 'BANNED'.
(Other definitions for banned that I've seen before include "Outlawed" , "Group on radio" , "Prohibited officially" , "Prohibited by censor" , "Forbidden by law" .)