Possibly felt it's not right (4)
I believe the answer is:
left
'not right' is the definition.
('left' is the opposite to 'right')
'possibly felt' is the wordplay.
'possibly' indicates anagramming the letters.
'felt' with letters rearranged gives 'LEFT'.
'it's' acts as a link.
(Other definitions for left that I've seen before include "Allowed to remain" , "The sinister side" , "Went; port" , "political group" , "Punch, perhaps" .)