Ninth Greek letter (4)
I believe the answer is:
iota
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ninth 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 iota that I've seen before include "Old letter" , "Hint" , "little part" , "Jot or tittle" , "letter from abroad" .)