Amorous gaze (4)
I believe the answer is:
'amorous gaze' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for leer that I've seen before include "Gaze lasciviously at" , "Suggestive or sneering look" , "Ogle, smirk" , "Stare suggestively" , "Suggestive or sneering grin" .)