Nick's angry about Conservative (5)
I believe the answer is:
score
'nick's' is the definition.
(thesaurus)
'angry about conservative' is the wordplay.
'angry' becomes 'sore' ('sore' can be similar in meaning to 'angry').
'about' means one lot of letters goes inside another.
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'sore' enclosing 'c' is 'SCORE'.
(Other definitions for score that I've seen before include "Tally; group of twenty" , "Reckoning" , "Grade; twenty" , "Music from film" , "Tally; 20" .)