Highly intelligent person is after university employment (5)
I believe the answer is:
usage
'employment' is the definition.
('usage' can be a synonym of 'employment')
'highly intelligent person is after university' is the wordplay.
'highly intelligent person' becomes 'sage'.
'is after' is a charade indicator (letters next to each other).
'university' becomes 'u'.
'sage' after 'u' is 'USAGE'.
(Other definitions for usage that I've seen before include "Employment - practice" , "Acceptable language" , "Particular meaning of a word" , "Habit" , "Terminology - custom" .)