Work required in shop, usually (4)
I believe the answer is:
opus
'work' is the definition.
(an opus is an artistic work)
'in shop usually' is the wordplay.
'in' says the answer is hidden in the clue.
'OPUS' is hidden within 'shop usually'.
'required' is the link.
(Other definitions for opus that I've seen before include "Work (mus.)" , "Musical piece" , "Artistic work" , "Work or composition, usually musical" , "Soup (anag.)" .)