Is hostile to female relative in conversation (4)
I believe the answer is:
anti
'is hostile to' is the definition.
(anti means hostile to or opposed to)
'female relative in conversation' is the wordplay.
'female relative' becomes 'auntie' (I've seen this before).
'in conversation' indicates a 'sounds like' (homophone) clue.
'auntie' sounds like 'ANTI'.
(Other definitions for anti that I've seen before include "not favoured" , "Opposition member" , "Negative vote" , "An opponent - opposed to party policy, etc" , "Person opposed" .)