Possible Clues:

• Hat has one mesmerised
• Hat of soft felt worn in London
• Showing outward strain, I left book and hat
• Du Maurier's novel headgear
• Hear about one-pound hat
• Hat — George du Maurier heroine
• One pound cut in tax? That's novel
• Endeavour to secure one pound for a hat
• Svengali's subject
• Go put one pound in hat