Westernmost Canadian territory (5)
I believe the answer is:
yukon
'westernmost canadian territory' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for yukon that I've seen before include "North American territory" , "part of Canada" , "Klondike region of Canada" , "Site of the Canadian gold rush of the 1890s" , "Canadian Gold Rush area" .)