Goody-goody (8)
I believe the answer is:
priggish
'goody-goody' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for priggish that I've seen before include "Self-righteously moralistic" , "Self-righteous, toffee-nosed" , "Sanctimonious" , "Smugly narrow-minded" , "Exaggeratedly proper" .)