Cocaine taken off freight ship (4)
I believe the answer is:
argo
'ship' is the definition.
(ship in Greek myth)
'cocaine taken off freight' is the wordplay.
'cocaine' becomes 'C' (drugs abbreviation).
'taken off' is a deletion indicator.
'freight' becomes 'cargo' (synonyms).
'cargo' with 'c' taken away is 'ARGO'.
(Other definitions for argo that I've seen before include "Ship used by Jason in his search for the Golden Fleece" , "Name of ship sailed by Jason in search of the Golden Fleece" , "Fabulous ship" , "Jason's craft" , "Jason's vessel" .)