Drugs in bits of footwear (6)
I believe the answer is:
uppers
This clue is a double definition.
'drugs' is the first definition.
(upper is a kind of drug)
'bits of footwear' is the second definition.
(upper is a part of a shoe)
'in' is the link.
(Other definitions for uppers that I've seen before include "Parts of shoes above the sole" , "the poor are on?" , "Out of luck, one may be on these" , "The 25 [PENNILESS] are on these" , "Drugs" .)