Italian river joins lake with country (6)
I believe the answer is:
poland
'country' is the definition.
(I know that Poland is a European country)
'italian river joins lake with' is the wordplay.
'italian river' becomes 'po' (river in Italy).
'joins' means one lot of letters go next to another.
'lake' becomes 'L' (geographical abbreviation).
'with' becomes 'and'.
'po'+'l'+'and'='POLAND'
(Other definitions for poland that I've seen before include "Wroclaw's country" , "Part of Europe" , "East European country" , "Country joining the European Union in 2004" , "Old pan (anag)" .)