Small parasite (4)
I believe the answer is:
mite
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">small parasite</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for mite that I've seen before include "The widow's small offering" , "Microscopic creature" , "Microscopic animal" , "Little chap" , "Child; a small amount" .)