Mark of perfection (3)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mark of perfection</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 ten that I've seen before include "Dudley Moore/Bo Derek film" , "Very young" , "Half a score" , "Five times two" , "Cardinal number" .)