Mine gas (8)
I believe the answer is:
firedamp
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mine gas</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that mine gas can be written as firedamp)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for firedamp that I've seen before include "Explosive gas in mines" , "Methane found in coal mines" , "Something potentially dangerous in mines" , "Combustible mixture" , "Methane in coalmines" .)