Bag search regularly omitted (3)
I believe the answer is:
sac
'bag' is the definition.
(a small bag)
'search regularly omitted' is the wordplay.
'regularly omitted' means one should take alternating letters (letters removed at regular intervals).
The alternate letters of 'search' are 'SAC'.
(Other definitions for sac that I've seen before include "Bodily pouch" , "Bag-like part of the body" , "Bodily cavity enclosed by a membrane" , "Bag, pouch; cyst" , "Pouch in the body" .)