Welding gas (9)
I believe the answer is:
acetylene
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">welding gas</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 acetylene that I've seen before include "Gas used chiefly in welding" , "Flammable gas" , "Illuminating stuff also used for joining" , "powers industrial torch" , "cutting gas emission?" .)