Volcanic material (4)
I believe the answer is:
lava
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">volcanic material</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for lava that I've seen before include "Volcanic discharge" , "Emanating magma" , "Volcanic emission" , "Outflow from volcano" , "Molten volcanic material" .)