Bitter about Conservative in buff (5)
I believe the answer is:
scour
'buff' is the definition.
(thesaurus)
'bitter about conservative' is the wordplay.
'bitter' becomes 'sour' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'conservative' becomes 'C' (UK political abbreviation).
'sour' placed around 'c' is 'SCOUR'.
'in' acts as a link.
(Other definitions for scour that I've seen before include "Clean by rubbing with an abrasive" , "scrub and scrape" , "Turn upside down" , "purge" , "Full" .)