Enlightenment may come so quickly! (2,1,5)
I believe the answer is:
in a flash
'quickly' is the definition.
(I've seen this in another clue)
'enlightenment may come so' is the wordplay.
I cannot really see how this works, but
'so' could be 'as' (e.g. phrases like 'not as tall' and 'not so tall') and 'as' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for in a flash that I've seen before include "pictures may be taken" , "Almost instantly" , "Instantly, straightaway" , "How lightning appears" , "Where American detected electricity" .)