Some replicas setter discovered in storage unit (8)
I believe the answer is:
cassette
'storage unit' is the definition.
'some replicas setter discovered' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'CASSETTE' is hidden in the letters of 'replicas setter discovered'.
'in' is the link.
(Other definitions for cassette that I've seen before include "Recording medium" , "Video" , "Container to go into tape deck" , "Music tape" , "something from old-fashioned language laboratory?" .)