Busy, even at university! (4,2)
I believe the answer is:
Here is my best explanation:
'busy' is the definition.
('tied up' can be similar in meaning to 'busy')
'even at university' is the subsidiary indication.
'even' becomes 'tied' ('tied' can be a synonym of 'even'**).
'at university' becomes 'up'.
(Another definition for tied up that I've seen is "Secured; engaged".)