Ring fashioned for a smile (4)
I believe the answer is:
grin
'a smile' is the definition.
('grin' can be a synonym of 'smile')
'ring fashioned' is the wordplay.
'fashioned' indicates an anagram.
'ring' with letters rearranged gives 'GRIN'.
'for' acts as a link.
(Other definitions for grin that I've seen before include "Smirk" , "Ring (anag.)" , "Toothy smile" , "show ivories happily with it" , "Happy expression" .)