Left on a map (4)
I believe the answer is:
west
'left on a map' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for west that I've seen before include "Mae -, US actress; W" , "Colombian with brews (anag)" , "English county" , "Dog (from Argyll?)" , "Small white dog" .)