Abstain from drug that is cut (6)
I believe the answer is:
eschew
'abstain from' is the definition.
(to eschew something is to avoid it)
'drug that is cut' is the wordplay.
'drug' becomes 'e' (E is another name for ecstasy).
'that is' becomes 'sc' (abbrv. for Latin scilicet; 'namely').
'cut' becomes 'hew' (hew can mean to chop or cut).
'e'+'sc'+'hew'='ESCHEW'
(Other definitions for eschew that I've seen before include "Steer clear of" , "Abstain from, shun" , "Deliberately avoid" , "'Avoid, keep away from (6)'" , "Avoid or abstain from (6)" .)