University to veto operating system (4)
I believe the answer is:
unix
'operating system' is the definition.
(UNIX operating system is an example)
'university to veto' is the wordplay.
'university' becomes 'u' (abbreviation for university).
'to veto' becomes 'nix' (I've seen this in another clue).
'u'+'nix'='UNIX'
(Other definitions for unix that I've seen before include "software" , "Computer open operating system" , "See this operating system" .)