Tenth letter of the Greek alphabet (5)
I believe the answer is:
kappa
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tenth letter of the greek alphabet</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for kappa that I've seen before include "letter from abroad" , "Greek character" , "10th Greek letter" , "Greek K" , "Letter before lambda" .)