Black substance in cigarettes (3)
I believe the answer is:
tar
'black substance in cigarettes' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tar that I've seen before include "Jack ..., British sailor" , "Sticky substance used in road construction" , "Informal sailor or road surfacing material" , "One sails on sea" , "one may need to pay on boat" .)