Fuels exciting things (5)
I believe the answer is:
gases
'things' is the definition.
The answer and definition can be both acts as well as being plural nouns.
Maybe there's a link between them I don't understand?
'fuels exciting' is the wordplay.
'fuels' becomes 'gas' (gas is a kind of fuel).
'exciting' becomes 'es' (I can't justify this - if you can you should give a lot more credence to this answer).
'gas'+'es'='GASES'
Can you help me to learn more?
(Other definitions for gases that I've seen before include "Vapours" , "Air-like fluids" , "Cruelly kills" , "Compressible fluids" , "Hydrogen and carbon monoxide, say" .)