Not in favour of female relative being on the radio (4)
I believe the answer is:
anti
'not in favour' is the definition.
(I've seen this before)
'female relative being on the radio' is the wordplay.
'female relative' becomes 'auntie' (I've seen this before).
'being on the radio' shows a homophone (sound like).
'auntie' sounds like 'ANTI'.
'of' acts as a link.
(Other definitions for anti that I've seen before include "(Person who is) not in favour" , "Definitely not pro" , "not favoured" , "Adversary" , "on the other side" .)