Crude cartel (4)
I believe the answer is:
opec
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">crude cartel</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for opec that I've seen before include "Group of petroleum producing countries, formed in 1961" , "Cartel of oil-producing countries" , "Group of oil-producing countries" , "Organisation intended to control the production and sale of petroleum" , "Group of countries with a common oil policy" .)