At university prom ahead of time (2,5)
I believe the answer is:
up front
'time' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'at university prom ahead' is the wordplay.
'at university' becomes 'up' (to 'come up' is to arrive for term, e.g. at Oxford).
'prom ahead' becomes 'front' (I can't explain this - if you can you should give a lot more credence to this answer).
'up'+'front'='UP-FRONT'
'of' acts as a link.
Can you help me to learn more?
(Another definition for up front that I've seen is " Honest - paid in advance".)