Snatch the odd small pouch (3)
I believe the answer is:
sac
'small pouch' is the definition.
(I've seen this in another clue)
'snatch the odd' is the wordplay.
'the odd' means one should take alternating letters.
The alternating letters of 'snatch' are 'SAC'.
(Other definitions for sac that I've seen before include "Bodily pouch" , "Bag-like cavity" , "Traditional entitlement to hold court" , "Bag-like part of the body" , "Pouch or bag-like structure" .)