A country sounded musical (6)
I believe the answer is:
grease
'musical' is the definition.
(Grease is a film musical)
'a country sounded' is the wordplay.
'a country' becomes 'Greece' (Greece is a European country).
'sounded' shows a homophone (sound like).
'greece' is a homophone of 'GREASE'.
(Other definitions for grease that I've seen before include "A thick oily substance" , "Fully aware, astonished" , "'Thick, fatty oil (6)'" , "-- gun; -- monkey" , "Possible cause of slip-up" .)