Why you, in a jiffy, see what's going to happen? (6,5)
I believe the answer is:
second sight
'why' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'you in a jiffy see what's going to happen?' is the wordplay.
I cannot really understand how this works, but
'jiffy' could be 'second' (I've seen this before) and 'second' is found within the answer.
'see' could be 'sight' (I've seen this before) and 'sight' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for second sight that I've seen before include "Something uncanny" , "aware of future potential?" , "ability to see ahead?" , "extraordinary ability" , "Clairvoyance" .)