Forgot ever holding back reject (4)
I believe the answer is:
veto
'reject' is the definition.
(thesaurus)
'forgot ever holding back' is the wordplay.
'holding' indicates the answer is hidden within the clue.
'back' says the letters should be written in reverse.
'otev' is hidden in the letters of 'forgot ever'.
'otev' backwards is 'VETO'.
(Other definitions for veto that I've seen before include "Embargo" , "Right to prevent proposed action" , "Refuse to endorse" , "Throw out" , "UN rejection" .)