Boxers perhaps used in fighting (6)
I believe the answer is:
undies
'boxers' is the definition.
(British slang for underwear)
'used in fighting' is the wordplay.
'fighting' indicates an anagram (I've seen this in other clues).
'used'+'in'='usedin'
'usedin' with letters rearranged gives 'UNDIES'.
'perhaps' acts as a link.
(Other definitions for undies that I've seen before include "Knickers (abbrev.)" , "Undergarments (colloq.)" , "Personal attire" , "Lingerie -- is nude (anag)" , "Used in (anag) -- unmentionables" .)