Carry Ecstasy into pub (4)
I believe the answer is:
bear
'carry' is the definition.
(bear can mean to transport or carry)
'ecstasy into pub' is the wordplay.
'ecstasy' becomes 'E' (informal term for the drug).
'into' is an insertion indicator.
'pub' becomes 'bar' (both are drinking establishments).
'e' inserted inside 'bar' is 'BEAR'.
(Other definitions for bear that I've seen before include "One's hairy" , "Abide; support" , "stand" , "Large carnivore" , "live with" .)