Moment – parasitic arachnid (4)
I believe the answer is:
tick
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">moment</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(both can mean a very short amount of time)</span><br/ ><br/ >'<span class="explanation-format__original">parasitic arachnid</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for tick that I've seen before include "Blood-sucking mite or parasitic insect" , "which is irritating!" , "Instant - credit" , "Insect; noise of watch" , "Parasitic insect or clicking sound" .)