Stuff to puff? (6)
I believe the answer is:
powder
This clue is a double definition.
'stuff' is the first definition.
(powder is a kind of stuff)
'to puff?' is the second definition.
(thesaurus)
(Other definitions for powder that I've seen before include "Solid substance in tiny loose particles" , "Small loose particles" , "Sort of keg, monkey, puff" , "Dust" , "Solid that has been pulverised" .)