Carried by shoppers, a carrier bag! (3)
I believe the answer is:
sac
'bag' is the definition.
(thesaurus)
'carried by shoppers a carrier' is the wordplay.
'carried by' indicates a hidden word.
'SAC' is hidden in the letters of 'shoppers a carrier'.
(Other definitions for sac that I've seen before include "Pouchlike structure" , "Pouch in the body" , "Bodily cavity enclosed by a membrane" , "Bag-like cavity" , "Pouch or bag-like structure" .)