Animal pouch (3)
I believe the answer is:
sac
'animal pouch' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sac that I've seen before include "Traditional entitlement to hold court" , "Pouch in the body" , "Pouchlike structure" , "Distended membrane; pouch-like cavity" , "Bladder" .)