Wide smile (4)
I believe the answer is:
grin
'wide smile' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for grin that I've seen before include "Cheeky smile" , "Smirk" , "Smile broadly showing teeth" , "Smile - all that could be seen of the vanishing Cheshire Cat" , "11 smile" .)