Supple smile - so different! (7)
I believe the answer is:
lissome
'supple' is the definition.
('lissome' can be a synonym of 'supple')
'smile so different' is the wordplay.
'different' is an anagram indicator.
'smile'+'so'='smileso'
'smileso' is an anagram of 'LISSOME'.
(Other definitions for lissome that I've seen before include "Willowy" , "Lithe; nimble" , "Oil mess (anag)" , "flexible" , "Slim, supple, graceful" .)