Constituent part (7)
I believe the answer is:
element
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">constituent part</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for element that I've seen before include "Basic constituent; aspect" , "Primary chemical substance" , "fire, perhaps, once" , "Constituent of universe" , "Iron, for instance - part of an electric kettle" .)