Possible Clues:

• Bowlers and trilbies
• Pillboxes and porkpies
• '___ off!'
• Dislikes losing energy in top gear
• Cowboys' headwear
• Stetsons and stovepipes
• What Dr. Seuss finds cats in
• The first words of 17- and 59-Across and 11- and 35-Down are kinds of them
• Fedoras and derbies
• Items to check