Filthy; sordid (7)
I believe the answer is:
squalid
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">filthy</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">sordid</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that sordid can be written as squalid)</span><br/ ><br/ ></span>
(Other definitions for squalid that I've seen before include "Wretched, filthy" , "Slum-like" , "run down" , "Seamy, sleazy" , "Extremely dirty" .)