Fifth Greek letter (7)
I believe the answer is:
epsilon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fifth greek letter</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for epsilon that I've seen before include "Greek letter - pinoles (anag)" , "Foreign character" , "One's lip (anag)" , "small number mispronounced, almost completely the wrong way round" , "character in Greece" .)