Scornful grin (5)
I believe the answer is:
sneer
'scornful grin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sneer that I've seen before include "Contemptuous remark" , "Smile contemptuously" , "Derisive remark" , "Dig" , "Show contempt by contorting the face" .)