Clergyman getting rid of cocaine immediately (4)
I believe the answer is:
anon
'immediately' is the definition.
(I've seen this before)
'clergyman getting rid of cocaine' is the wordplay.
'clergyman' becomes 'canon' (canon is a kind of clergyman).
'getting rid of' suggests deleting specific letters.
'cocaine' becomes 'c' (drugs abbreviation).
'canon' with 'c' taken away is 'ANON'.
(Other definitions for anon that I've seen before include "Of unknown authorship" , "Soon, shortly (archaic)" , "Soon, precious stone" , "Soon or presently" , "before long" .)