Chuck Norris wants to fight, ultimately making a comeback (4)
I believe the answer is:
toss
'chuck' is the definition.
('toss' can be a synonym of 'chuck')
'norris wants to fight ultimately making a comeback' is the wordplay.
'ultimately' indicates one should take the final letters.
'making a comeback' is a reversal indicator.
The final letters of 'norris wants to fight' are 'ssot'.
'ssot' reversed gives 'TOSS'.
(Other definitions for toss that I've seen before include "Raise a bit of money before opening" , "Fall from horse" , "Chuck" , "Throw tt" , "have a restless night, perhaps" .)