Old-fashioned engine driver (5)
I believe the answer is:
steam
I believe this clue is a double definition.
'old-fashioned' is the first definition.
(I've seen this before)
'engine driver' is the second definition.
(a steam engine is powered by steam)
(Other definitions for steam that I've seen before include "Energy (colloq.)" , "Vapour from water at boiling point" , "It's water mist, mates" , "Invisible gas from boiling water" , "get very angry" .)