Even — out of tune (4)
I believe the answer is:
flat
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">even</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">out of tune</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for flat that I've seen before include "place to live" , "Even -- pitched too low" , "Not hilly" , "Personal residence" , "Uninteresting - piece of scenery" .)