Explosive initiator (9)
I believe the answer is:
detonator
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">explosive initiator</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 detonator that I've seen before include "cap" , "Explosion starter" , "Explosive initiator" , "Part of bomb" , "small charge" .)