City tribe rioting outside university (6)
I believe the answer is:
beirut
'city' is the definition.
(Beirut is an example)
'tribe rioting outside university' is the wordplay.
'rioting' indicates an anagram.
'outside' means one lot of letters goes inside another.
'university' becomes 'u' (abbreviation for university).
'tribe' is an anagram of 'beirt'.
'beirt' placed around 'u' is 'BEIRUT'.
(Other definitions for beirut that I've seen before include "Lebanese capital" , "Middle East capital" , "Lebanon's capital" , "Capital city of Lebanon" , "Capital of 21 across" .)