It will draw on oxygen to ignite an engine (7)
I believe the answer is:
magneto
This might be a double definition.
'it will draw on oxygen to ignite an' is the first definition.
The definition suggests a singular noun which matches the answer.
'engine' is the second definition.
(I know that magneto is a type of generator)
Can you help me to learn more?
(Other definitions for magneto that I've seen before include "Small type of generator" , "Ignition apparatus" , "engine part" , "Small electric generator" , "generation device" .)