I as in Ithaca (4)
I believe the answer is:
iota
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">i as in ithaca</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 "Smidgen" , "Just a jot, from Greek alphabet" , "Old letter" , "Scintilla" , "Trace" .)