Greek town, once home to the oracle, Pythia (6)
I believe the answer is:
delphi
(Other definitions for delphi that I've seen before include "Greek site of Apollo's most famous oracle" , "'Ancient Greek city, site of the oracle (6)'" , "Scene of ancient oracle" , "Home of the oracle on the slopes of Mount Parnassus" , "Where Apollo's most famous oracle spoke in Greece" .)