Smile smugly (5)
I believe the answer is:
smirk
'smile smugly' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for smirk that I've seen before include "Compacent smile" , "Irritating smile" , "Self-satisfied smile" , "Smug look" , "Self-satisfied grin" .)