At university, retain maintenance (6)
I believe the answer is:
upkeep
'maintenance' is the definition.
(I know that maintenance can be written as upkeep)
'at university retain' is the wordplay.
'at university' becomes 'up' (slang term meaning at university).
'retain' becomes 'keep' (synonyms).
'up'+'keep'='UPKEEP'
(Other definitions for upkeep that I've seen before include "Looking after" , "Running costs" , "Cost of support" , "Cost of maintaining" , "Cost of maintenance, say household" .)