Pouch-like structure (3)
I believe the answer is:
sac
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">pouch-like structure</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 sac that I've seen before include "Bag-like part of the body" , "Bladder" , "Distended membrane; pouch-like cavity" , "Pouch in the body" , "Bag-like part in animal or plant" .)