Fed up about the setter's flipping fault (7)
I believe the answer is:
demerit
'fault' is the definition.
(synonyms)
'fed up about the setter's flipping' is the wordplay.
'fed up' becomes 'tired'.
'about' is an insertion indicator.
'the setter' becomes 'me' (the setter of the clue).
'flipping' is a reversal indicator.
'tired' placed around 'me' is 'tiremed'.
'tiremed' back-to-front is 'DEMERIT'.
(Other definitions for demerit that I've seen before include "Fault, defect" , "Something deserving censure" , "Mark given for a fault" , "Black mark" , "Conduct that deserves censure" .)