Possible Clues:

• 'Ancient Greek city, site of the oracle (6)'
• Classical scene of Apollo topping brothers
• It's all for the best, by the look of it
• Source of good advice gleaned from Prince in Asian capital
• Where I'd be about to help with the oracle
• 'In Greek mythology, the site of the oracle (6)'
• Sacred site of power in Indian city
• I'd be about to help you here in an oracular manner
• Home of the oracle on the slopes of Mount Parnassus
• Some model philosophers cover riddler's retreat