Long loose overcoat (6)
I believe the answer is:
ulster
'long loose overcoat' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ulster that I've seen before include "Long loose overcoat, from the province?" , "Overcoat; Irish region" , "Cloak for an Irish province" , "Overcoat; former kingdom in Ireland" , "old province" .)