Related Clues:

• Haberdashery buys
• They may be tipped in acknowledgment
• Busby and derby
• Milliner's inventory
• Bonnet, perhaps, hides top set of wheels
• Capital investment
• Hats, etc
• Hat(s)
• 'Porkpie' and 'pillbox' attire
• They may be passed or tipped
• Hats, hoods and helmets
• Principal stuff, like a mortar board perhaps
• Berets and sombreros
• Roles, in metaphor
• Football helmet, e.g