Minute fragment (4)
I believe the answer is:
atom
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">minute fragment</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 atom that I've seen before include "A small but mighty particle" , "Tiny particle, great bomb" , "The tiniest particle" , "Very small object or amount" , "Small amount of matter" .)