Fair amount of omen from spirit is ultimately false or it's a powerful source for movement? (6)
I believe the answer is:
Here is my best explanation:
'fair amount of omen' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'spirit is ultimately false or it's a powerful source for movement?' is the wordplay.
I cannot quite understand how this works, but
'spirit' could be 'gin' (I've seen this before) and 'gin' is present in the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found within the answer.
The remaining letters 'ne' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'from' is the link.
(Other definitions for engine that I've seen before include "eg Nine (anag.)", "turn of mind once", "Locomotive", "Machine doing work", "Mechanical device as source of power, a driver", "Motive machine", "Source of power", "It converts energy to motion", "Power source" and "Machine with moving parts".)