Grins (6)
I believe the answer is:
smiles
'grins' is the definition.
('smile' can be a synonym of 'grin')
This is all the clue.
(Other definitions for smiles that I've seen before include "expresses pleasure" , "Beams, grins" , "Gives visible sign of pleasure" , "Shows signs of pleasure or amusement" , "Facial expressions showing pleasure" .)