Dirty talk of a cinder (4)
I believe the answer is:
smut
This clue is a double definition.
'dirty talk' is the first definition.
(I've seen this before)
'a cinder' is the second definition.
(thesaurus)
'of' is the link.
(Other definitions for smut that I've seen before include "Small flake of dirt" , "Obscene material" , "Pornographic material" , "Obscene filth" , "Indecent items or talk" .)