Dirty, grimy (6)
I believe the answer is:
grubby
I believe this is a double definition.
'dirty' is the first definition.
(similar in meaning)
'grimy' is the second definition.
(I know that grimy can be written as grubby)
(Other definitions for grubby that I've seen before include "Dirty or unwashed, as urchin may be" , "Squalid" , "Covered with ingrained dirt" , "Soiled" , "Dirty, grimy" .)