Fuel derived from coal (4)
I believe the answer is:
coke
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fuel derived from coal</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for coke that I've seen before include "Carbon fuel" , "Furnace fuel" , "Carbonised fuel residue" , "something for heating" , "'Soft drink and hard drug, in short (4)'" .)