Burnt matter (3)
I believe the answer is:
ash
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">burnt matter</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 ash that I've seen before include "Tree; cinders" , ". . . . [FOREST] One of which" , "Remnant from fire" , "Silvery-grey" , "In fireplace it may be" .)