Possible Clues:

• Papal letter
• Letter addressed by the Pope to all his bishops
• Pope's letter
• Key to new and regularly repeated series comes from father in Rome
• Misspelling of 'clay' in abbreviated ecclesiastical letter from Vatican
• Half open seasonal letter posted in Rome perhaps
• Bishops can get this cycling endlessly about in back lane
• Letter from Rome admits breakdown of New York City in CIA cell
• Papal letter nicely amended to include Conservative state
• Papal letter in Parisian style arranged in a ring