Ancient city in Italy buried by an eruption of Vesuvius (7)
I believe the answer is:
pompeii
(Other definitions for pompeii that I've seen before include "City buried by Vesuvius eruption" , "City buried by volcanic eruption, AD 79" , "Italian city, buried by volcanic ash 79 AD" , "Ancient city near Naples destroyed by volcano" , "Ancient town near Naples buried by volcanic ash" .)