Not odd (4)
I believe the answer is:
even
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not odd</span>' is the definition.<br/ ><span class="explanation-format__explanation">('even' is the opposite to 'odd')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for even that I've seen before include "Tied" , "Pantomime" , "Level, equal" , "Not bumpy" , "without a rise?" .)