Club attended by academic rival, now and then, is in Balkan region (9)
I believe the answer is:
macedonia
'balkan region' is the definition.
(region of Europe)
'club attended by academic rival now and then' is the wordplay.
'club' becomes 'mace' (mace can mean a club or stick).
'attended by' means one lot of letters go next to another.
'academic' becomes 'don' (type of academic - especially at Oxbridge).
'now and then' means one should take alternating letters (letters taken on a regular basis, now and then).
The alternating letters of 'rival' are 'ia'.
'mace'+'don'+'ia'='MACEDONIA'
'is in' is the link.
(Other definitions for macedonia that I've seen before include "Southeast European country" , "Landlocked Balkan country" , "Alexander the Great's homeland" , "European country, capital Skopje" , "republic" .)