Coat of filth (5)
I believe the answer is:
grime
(Other definitions for grime that I've seen before include "an ingrained phenomenon" , "Ingrained dirt" , "Dirt, grease" , "Engrained dirt" , "Soot" .)
I believe the answer is:
grime
(Other definitions for grime that I've seen before include "an ingrained phenomenon" , "Ingrained dirt" , "Dirt, grease" , "Engrained dirt" , "Soot" .)