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