Quietly returned cigarettes and beer of old Greeks (8)

'of old greeks' is the definition.
(relating to the ancestors of the ancient Greeks)

'quietly returned cigarettes and beer' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'returned' shows that the letters should be reversed in order.
'cigarettes' becomes 'cigs' (short for cigarettes).
'and' is a charade indicator (letters next to each other).
'beer' becomes 'ale' (type of beer).
'cigs'+'ale'='cigsale'
'cigsale' reversed gives 'elasgic'.
'p'+'elasgic'='PELASGIC'