Aviation spirit (7)
I believe the answer is:
gremlin
This could be a double definition.
'aviation' is the first definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'spirit' is the second definition.
(I have seen 'Mischievous spirit' mean 'gremlin' so perhaps 'spirit' could also mean 'gremlin')
Can you help me to learn more?
(Other definitions for gremlin that I've seen before include "Mischievous machine saboteur" , "Mingler that causes damage to machinery" , "Fault-inducing sprite" , "One sabotages" , "Cause of technical fault" .)