Long overcoat (6)
I believe the answer is:
ulster
'long overcoat' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ulster that I've seen before include "A heavy coat" , "Overcoat; Irish region" , "Ancient northern Irish kingdom" , "Overcoat; N. Ireland" , "former province of Ireland" .)