Armed fighting (6)
I believe the answer is:
combat
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">armed fighting</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for combat that I've seen before include "War; contest" , "Battle or fight" , "Military action" , "Fight - strive against" , "Fight against; fighting" .)