Suggestive or sneering look (4)
I believe the answer is:
leer
'suggestive or sneering look' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for leer that I've seen before include "Suggestive or sneering look" , "Suggestive or sneering grin" , "Look lasciviously at" , "Lecherous look" , "Look lecherously" .)