Enlightenment may come so quickly! (2,1,5)
I believe the answer is:
in a flash
'quickly' is the definition.
Both the answer and definition are adverbs. Maybe you can see an association between them that I don't see?
'enlightenment may come so' is the wordplay.
I cannot quite see how this works, but
'so' could be 'as' (I've seen this in other clues) and 'as' is present in the answer.
This may be the basis of 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" .)