Stare lasciviously (4)
I believe the answer is:
leer
'stare lasciviously' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for leer that I've seen before include "Stare suggestively" , "Lecherous look" , "Suggestive or sneering grin" , "Give sly look" , "Lascivious gaze" .)