Possible Clues:

• Overturn
• Turn turtle
• Flip over
• Overturn a boat
• How big does the headgear have to be so as to turn it over?
• Flip
• Covers eyes, we hear, to turn over
• Overturn possible indication of conceitedness
• What for a big-headed chap is a large number to upset
• Upset glue, lid needs to be put on first