Part of a Mountie uniform (7)
I believe the answer is:
stetson
'part of a mountie uniform' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for stetson that I've seen before include "Style of hat" , "Felt hat" , "Large hat" , "Capital investment" , "Hat, for Texan oil magnate, say" .)