Possible Clues:

• Big hit on the lecture circuit
• Signal folder can provide something enthralling
• Fascinating orator — ill-bred pens (anag)
• Captivating orator to read out letters, having file of documents
• Orator to provide series of letters for someone making a book?
• Mesmerizing speaker
• One entrancing period of work on farm machinery
• After some time, craftsman finishing book that's fascinating
• Enchanting person's period in front of reaping-machine
• Arresting speaker some time on file