Downfall of game island country (9)
I believe the answer is:
ruination
'downfall' is the definition.
(I know that downfall can be written as ruination)
'game island country' is the wordplay.
'game' becomes 'RU' (rugby union).
'island' becomes 'i' (geographical abbreviation).
'country' becomes 'nation' (synonyms).
'ru'+'i'+'nation'='RUINATION'
'of' is the link.
(Other definitions for ruination that I've seen before include "Utter destruction" , "total disaster" , "Complete downfall" , "End" , "Complete destruction or collapse" .)