Instrument of attack (6)
I believe the answer is:
weapon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">instrument of attack</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 "Object to fight with" , "club, perhaps" , "Object used in fighting" , "Instrument of war" , "Instrument to inflict harm" .)