Clue: Magistrate touring great old city, one in India (6)
Answer: JAIPUR
Explanation: Definition: one in India
A charade of JAIP, an envelope ('touring') of AI (A1, 'great') in JP (Justice of the Peace, 'magistrate'); plus UR ('old city'). Irrelevant to the clue. but Ai is also an old city, mentioned in the Book of Joshua.