Propane, for one (3)
I believe the answer is:
gas
'propane for one' is the definition.
(propane is a kind of gas)
This is the entire clue.
(Other definitions for gas that I've seen before include "American fuel" , "Neon, for example" , "Something delightful" , "What's needed to drive" , "State of matter not solid or liquid" .)