Fabric used by a hospital intern (4)
I believe the answer is:
lint
'fabric' is the definition.
(lint is a kind of fabric)
'by a hospital intern' is the wordplay.
'by a' says the answer is hidden in the clue.
'LINT' is hidden in the letters of 'hospital intern'.
'used' is the link.
(Other definitions for lint that I've seen before include "Wound dressing" , "Napped cloth used to dress wounds" , "Wound-dressing fabric" , "Soft cloth for dressing wounds" , "Soft material for dressing wounds" .)