Cloud of insects (5)
I believe the answer is:
swarm
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">cloud of insects</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 swarm that I've seen before include "New colonists" , "many insects" , "Mob" , "Large group of flying insects" , "Body of bees" .)