Wingless parasites (4)
I believe the answer is:
lice
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">wingless parasites</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for lice that I've seen before include "Parasitic insects" , "Bloodsucking insects" , "Crawlers" , "Wingless bloodsucking parasites" , "Bloodsucking parasitic insect" .)