Slight hint, possibly (4)
I believe the answer is:
thin
'slight' is the definition.
(similar in meaning)
'hint possibly' is the wordplay.
'possibly' is an anagram indicator.
'hint' anagrammed gives 'THIN'.
(Other definitions for thin that I've seen before include "Insubstantial" , "Implausible" , "Slender, slight" , "Made of light material" , "Fine" .)