Some Greek letters (3)
I believe the answer is:
nus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">some greek letters</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 nus that I've seen before include "students" , "Greek letters, N" , "Letters from abroad" .)