__-mo (3)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mo</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 sec that I've seen before include "Mo or min?" , "Twinkling" , "(Of wines) dry" , "very short space of time" , "'Dry, as wine (3)'" .)