Oil cartel (4)
I believe the answer is:
opec
'oil cartel' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for opec that I've seen before include "Group of oil-producing countries" , "price-fixers?" , "[CRUDE OIL] suppliers?" , "Group of countries with a common oil policy" , "Cartel of oil-producing countries" .)