Fail to take advantage of reasonable mark at university (4,2)
I believe the answer is:
pass up
'fail to take advantage of' is the definition.
(I've seen this before)
'reasonable mark at university' is the wordplay.
'reasonable mark' becomes 'pass' (I can't explain this - if you can you should believe this answer much more).
'at university' becomes 'up' (to 'come up' is to arrive for term, e.g. at Oxford).
'pass'+'up'='PASS UP'
Can you help me to learn more?
(Other definitions for pass up that I've seen before include "Neglect (an opportunity)" , "Refrain from seizing (an opportunity)" , "forego" , "Ignore" , "Refrain from taking an opportunity" .)