Sap-sucking insect (5)
I believe the answer is:
aphid
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sap-sucking insect</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 aphid that I've seen before include "plant pest" , "Small plant-sucking insect" , "Insect feeding on plant juices" , "Plant louse" , "one living on juices" .)