Work in shop usefully (4)
I believe the answer is:
opus
'work' is the definition.
(I've seen this before)
'in shop usefully' is the wordplay.
'in' says the answer is hidden in the clue.
'OPUS' is hidden in the letters of 'shop usefully'.
(Other definitions for opus that I've seen before include "Composition - magnum __" , "Artistic work" , "Musical piece" , "A Latin work" , "Work (of a composer?)" .)