Tiny piece of matter (8)
I believe the answer is:
particle
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tiny piece of 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 particle that I've seen before include "Small amount" , "Tiny amount" , "Small unit of matter" , "Tiny piece of anything" , "Minute fragment" .)