Bag regularly found in search (3)

I believe the answer is:

sac

'bag' is the definition.
(thesaurus)

'regularly found in search' is the wordplay.
'regularly found in' indicates alternate letters.
The alternating letters of 'search' are 'SAC'.

(Other definitions for sac that I've seen before include "Pouch or bag-like structure" , "Pouch in the body" , "Animal or vegetable pouch" , "Bladder" , "Bag, pouch; cyst" .)

I've seen this clue in The Times.

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