Leftover matter (7)
I believe the answer is:
residue
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">leftover matter</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 residue that I've seen before include "Whatever is left over" , "Surplus" , "Part remaining" , "Remainder, leftover" , "Small amount remaining" .)