Fighter needing some adrenaline (3)
I believe the answer is:
ali
'fighter' is the definition.
(boxer Muhammad Ali)
'some adrenaline' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'ALI' is hidden within 'adrenaline'.
'needing' is the link.
(Other definitions for ali that I've seen before include "Muhammad ..., former boxer" , "Muhammad ..., famous boxer" , ""The Greatest" boxer" , "Dickens novel" , "Person" .)