Related Clues:

• Letter distribution on a base
• "Junk" that goes third-class
• Protective plating
• Knight clothing
• Lancelot's strong suit?
• 'You've got --'
• Postman on the phone
• Common delivery
• Some plane cargo
• A lot of it is first-class
• Irish boy returning to post
• Armour; post
• Letters; armour
• Sound fellow in flexible armour
• Letters man read out