Possible Clues:

• It's part of the mail
• Item on a letter (2 words)
• Collectible item bought originally for a penny
• Coach in job a 1 Across means to secure delivery
• Sounds like it¿s one of those instructions in 14 across for getting your message over? Lick that!
• Mail sticker
• First four characters in 14 across take a long time to get Frank in the corner after getting licked
• Token stuck on a letter — ATM stoppages (anag)
• Put one's foot down after Gestapo trashed collector's item
• 'Forever' item