Organism that lives on another (8)
I believe the answer is:
parasite
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">organism that lives on another</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for parasite that I've seen before include "It lives off its host" , "host has to put up with" , "Twenty five dn [LEECH]" , "Possibly tick" , "It depends on the host" .)