Working instrument (4)
I believe the answer is:
tool
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">working 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 tool that I've seen before include "Maybe saw" , "Instrument, implement" , "Cat's-paw; impress design on" , "Hand implement" , "Person exploited" .)