Fighting instrument (6)
I believe the answer is:
weapon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fighting instrument</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for weapon that I've seen before include "Instrument of offence or defence" , "A tool for inflicting injury" , "shooter, say" , "Instrument of attack or defence" , "club, perhaps" .)