Refuse to accept it's rejected fate (7)
I believe the answer is:
destiny
'fate' is the definition.
('destiny' can be a synonym of 'fate')
'refuse to accept it's rejected' is the wordplay.
'refuse' becomes 'deny' ('deny' can be a synonym of 'refuse'**).
'to accept' is an insertion indicator.
'rejected' is a reversal indicator.
'its' in reverse letter order is 'sti'.
'deny' going around 'sti' is 'DESTINY'.
(Other definitions for destiny that I've seen before include "portion" , "Ultimate fate" , "Fortune" , "Kismet, fate" , "must?" .)