Solvent spilled at once (6)
I believe the answer is:
octane
'solvent' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'spilled at once' is the wordplay.
'spilled' indicates anagramming the letters.
'at'+'once'='atonce'
'atonce' anagrammed gives 'OCTANE'.
Can you help me to learn more?
(Other definitions for octane that I've seen before include "Fuel component in McLaren vehicle" , "Anti-knock rating" , "Petrol quality rating" , "A liquid hydrocarbon found in petroleum" , "Ingredient of petroleum" .)