Self-righteous person (4)
I believe the answer is:
prig
'self-righteous person' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for prig that I've seen before include "Self-righteous moralist" , "Old maid" , "Sanctimonious person" , "Unpleasant arrogant person" , "Straight-laced person" .)