Cart coins off to get drugs (9)
I believe the answer is:
narcotics
'drugs' is the definition.
(I know this)
'cart coins off' is the wordplay.
'off' indicates anagramming the letters.
'cart'+'coins'='cartcoins'
'cartcoins' anagrammed gives 'NARCOTICS'.
'to get' is the link.
(Other definitions for narcotics that I've seen before include "Drugs that cause sleep or drowsiness" , "Stupefying drugs" , "Addictive drugs" .)