Related Clues:

• Sudden thought
• Dome light?
• Fully-grown germ?
• Creative starting point
• 'You have no ___!'
• Something to think up
• It can be big or harebrained
• [Lightbulb!]
• Invention preceder
• On-bulb, symbolically
• It's never been thought of before
• Notion in the mind
• A thought or notion
• Notion, thought
• Notion, image