Greek letter E (7)
I believe the answer is:
epsilon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">greek letter e</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 epsilon that I've seen before include "Greek letter E" , "Greek short E" , "character in Greece" , "Greek letter - pinoles (anag)" , "Greek character" .)