Winner to nag about European bubbly (9)
I believe the answer is:
champagne
'bubbly' is the definition.
(I know that bubbly can be written as champagne)
'winner to nag about european' is the wordplay.
'winner' becomes 'champ' (I've seen this before).
'to' is a charade indicator (letters next to each other).
'about' is an anagram indicator.
'european' becomes 'E' (abbreviation e.g. EU).
'nag' anagrammed gives 'agn'.
'champ'+'agn'+'e'='CHAMPAGNE'
(Other definitions for champagne that I've seen before include "French 'sparkler'" , "French wine district" , "Sparkling wine of north-eastern France" , "part of France" , "Someone whose life style belies their professed radical politics" .)