Old fighter somewhat exhilaratingly knocked back (3)
I believe the answer is:
ali
'old fighter' is the definition.
(I've seen this before)
'somewhat exhilaratingly knocked back' is the wordplay.
'somewhat' indicates the answer is hidden within the clue.
'knocked back' is a reversal indicator.
'ila' can be found hidden inside 'exhilaratingly'.
'ila' reversed gives 'ALI'.
(Other definitions for ali that I've seen before include "Muhammad - - , legendary boxer" , "Champion of ring" , "Muhammad's son-in-law" , "Muhammad --, US boxer" , "Muhammad ___ (or MacGraw?)" .)