Clue: Italian town, unaltered over centuries, at last beginning to industrialise (6)
Answer: ASSISI
Explanation: Italian town, unaltered over centuries, at last beginning to industrialise (6)
A charade of ASSIS, an envelope ('over') of S ('centurie**S** at last') in AS IS ('unaltered'); plus I ('beginning to **I**ndustrialise').