Dull, monotonous (7)
I believe the answer is:
humdrum
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">dull</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">monotonous</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that monotonous can be written as humdrum)</span><br/ ><br/ ></span>
(Other definitions for humdrum that I've seen before include "Common place" , "Boringly monotonous" , "Run-of-the-mill" , "Run of the mill" , "Mundane, commonplace" .)