Fuel type (6)
'fuel type' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for diesel that I've seen before include "Eponymous German engineer" , "See lid for the engine" , "Train perhaps" , "Motor fuel" , "See lid, oddly, of the fuel" .)
'fuel type' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gas that I've seen before include "Oxygen is one" , "Substance like air" , "It's not liquid or solid, like American petrol" , "Chatter (colloq.)" , "Something exciting" .)