Female fighter, extremely capable (5)
I believe the answer is:
alice
'female' is the definition.
(woman's name)
'fighter extremely capable' is the wordplay.
'fighter' becomes 'Ali' (boxer Muhammad Ali).
'extremely' means to remove the middle letters (only the extremes of the word are used).
'capable' with its centre taken out is 'ce'.
'ali'+'ce'='ALICE'
(Other definitions for alice that I've seen before include "Carroll heroine" , "Wonderland heroine" , "Lewis Carroll's immortal girl" , "Movement" , "band" .)