Dull or commonplace (10)
I believe the answer is:
pedestrian
<span class="explanation-format__ClueExplanation">This clue 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">commonplace</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for pedestrian that I've seen before include "he goes for a walk" , "Walker; prosaic" , "Hiker" , "lame" , "flat" .)