Feeling smart about Conservative account (5)
I believe the answer is:
score
'account' is the definition.
(I know that account can be written as score)
'feeling smart about conservative' is the wordplay.
'feeling smart' becomes 'sore' (a smart can mean a pain).
'about' indicates putting letters inside.
'conservative' becomes 'C' (UK political abbreviation).
'sore' enclosing 'c' is 'SCORE'.
(Other definitions for score that I've seen before include "Hit - music" , "Result" , "Tally in a game" , "Put ball in the net" , "Grade; twenty" .)