River, lake and country (6)
I believe the answer is:
poland
'country' is the definition.
(I know that Poland is a European country)
'river lake and' is the wordplay.
'river' becomes 'Po' (Italian river).
'lake' becomes 'L' (geographical abbreviation).
'po'+'l'+'and'='POLAND'
(Other definitions for poland that I've seen before include "Old pan (anag)" , "Wroclaw's country" , "Part of Europe" , "East European country" , "Its capital is Warsaw" .)