Civilised European drinking Vermouth (6)
I believe the answer is:
polite
'civilised' is the definition.
(I know that civilised can be written as polite)
'european drinking vermouth' is the wordplay.
'european' becomes 'pole' (someone from Poland).
'drinking' means one lot of letters goes inside another (inserted letters are consumed or drunk).
'vermouth' becomes 'it' (short for 'Italian vermouth' as in 'gin and it').
'pole' enclosing 'it' is 'POLITE'.
(Other definitions for polite that I've seen before include "Of courteous manners" , "Not rude" , "Cultured, refined" , "Well-mannered, courteous" , "Good mannered and civil" .)