Approval after turning on corner (4)
I believe the answer is:
nook
'corner' is the definition.
(synonyms)
'approval after turning on' is the wordplay.
'approval' becomes 'ok' (OK is an example).
'after' is a charade indicator (letters next to each other).
'turning' says the letters should be written in reverse.
'on' backwards is 'no'.
'ok' after 'no' is 'NOOK'.
(Other definitions for nook that I've seen before include "Cranny or niche" , "Interior angle formed where two walls meet" , "Alcove" , "Comfortable corner" , "Quiet corner" .)