Found us toying with soot (4)
I believe the answer is:
dust
'soot' is the definition.
(thesaurus)
'found us toying with' is the wordplay.
'with' says the answer is hidden in the clue.
'DUST' is hidden in the letters of 'found us toying'.
(Other definitions for dust that I've seen before include "Powdery dirt in dry areas" , "Powdery matter" , "Hopes to turn to this" , "Clean; fine powder" , "Fine dirt particles" .)