Divisible by 2 (4)
I believe the answer is:
even
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">divisible by 2</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 even that I've seen before include "When darkness starts to fall" , "Level, calm" , "Flush" , "Like 2,4,6, ..." , "Level, straight or regular" .)