Related Clues:

• Head piece?
• Creator's sine qua non
• Brainchild
• Theory
• It comes to a head
• Creative nugget
• Exclamation point?
• Inventor's "step one"
• Sneaking suspicion
• Theme
• Result of cogitating
• Bean product?
• Gray matter output
• Entrepreneur's start
• 'The very ___!'