Fabric used in dressing (4)
I believe the answer is:
lint
This clue is a double definition.
'fabric' is the first definition.
(I know that lint is a type of fabric)
'dressing' is the second definition.
(material used for dressing wounds)
'used in' acts as a link.
(Other definitions for lint that I've seen before include "Fabric for dressing wounds" , "Fabric for dressings" , "Wound-dressing fabric" , "Soft cloth for dressing wounds" , "Napped cloth used to dress wounds" .)