Proper's partner (4)
I believe the answer is:
prim
'proper's partner' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for prim that I've seen before include "Proper (type of rose?)" , "Prudish, formal" , "Old-maidish" , "Prudishly disapproving" , "Prudish, proper" .)