Flat, uniform (4)
I believe the answer is:
even
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">flat</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(level)</span><br/ ><br/ >'<span class="explanation-format__original">uniform</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(both can mean equal or level)</span><br/ ><br/ ></span>
(Other definitions for even that I've seen before include "That's not odd" , "Flat - yet" , "Pantomime" , "Like 2,4,6, ..." , "Flat, level" .)