Covers used in drugstores (4)
I believe the answer is:
rugs
'covers' is the definition.
(rug is a kind of cover)
'in drugstores' is the wordplay.
'in' indicates the answer is hidden within the clue.
'RUGS' can be found hidden inside 'drugstores'.
'used' is the link.
(Other definitions for rugs that I've seen before include "Floor mats or thick blankets" , "Floor covering" , "Wigs?" , "Carpets" .)