Small flake of soot (4)
I believe the answer is:
smut
(Other definitions for smut that I've seen before include "Obscene talk" , "Soot, dirt, grit" , "Indecent items or talk" , "Particle of dirt" , "porn?" .)
I believe the answer is:
smut
(Other definitions for smut that I've seen before include "Obscene talk" , "Soot, dirt, grit" , "Indecent items or talk" , "Particle of dirt" , "porn?" .)