Related Clues:

• Good-humoured teasing
• Frivolity, lightweight laughter
• Light teasing repartee
• Flippant attitude to serious matters
• Lack of seriousness
• Might trains get to rely on such banter?
• Banter about the train service, perhaps?
• Banter for training, perhaps
• Sounds as if perhaps one might need training for such banter
• Perhaps training for banter
• Ridicule this by train, perhaps
• Putting it in a sort of tax is nothing serious
• Mockingbird with lyre-shaped tail
• It's frivolous having a tax about it
• Impose about it with light-heartedness