Big cocaine bust (7)
I believe the answer is:
oceanic
'big' is the definition.
(similar in meaning)
'cocaine bust' is the wordplay.
'bust' is an anagram indicator.
'cocaine' is an anagram of 'OCEANIC'.
(Other definitions for oceanic that I've seen before include "vast waves?" , "Of the open sea" , "Relating to the high seas" , "Pelagic" , "Pertaining to the sea" .)