Excessive anger, leaving university too young (8)
I believe the answer is:
underage
'too young' is the definition.
(I've seen this before)
'excessive anger' is the wordplay.
'excessive' becomes 'unde' (I can't explain this - if you can you should give a lot more credence to this answer).
'anger' becomes 'rage' (rage is a kind of anger).
'unde'+'rage'='UNDERAGE'
'leaving university' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for underage that I've seen before include "one too young" , "Need a rug (anag.)" , "Not legally old enough" , "Not old enough to exercise legal right" , "Immature" .)