Wise man supports university practice (5)
I believe the answer is:
usage
'practice' is the definition.
(usage is a kind of practice)
'wise man supports university' is the wordplay.
'wise man' becomes 'sage' (sage is a kind of wise man).
'supports' says to put letters next to each other (bottom letters provide a support for the top ones).
'university' becomes 'u'.
'sage' put after 'u' is 'USAGE'.
(Other definitions for usage that I've seen before include "Customary way in which language is spoken or written" , "Treatment; tradition" , "etiquette" , "Common practice" , "Particular meaning of a word" .)