Conservative opponent goes around greeting a red (7)
I believe the answer is:
chianti
'a red' is the definition.
(I know that Chianti is a red)
'conservative opponent goes around greeting' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'opponent' becomes 'anti' (someone opposed to something).
'goes around' means one lot of letters goes inside another.
'greeting' becomes 'hi' (hi is a kind of greeting).
'c'+'anti'='canti'
'canti' placed around 'hi' is 'CHIANTI'.
(Other definitions for chianti that I've seen before include "I can hit for popular Italian wine" , "Chain it to popular Italian wine" , "Italian wine - mountain range" , "Dry red Italian wine" , "Italian wine variety" .)