Related Clues:

• Mental glimmer
• Object of thought
• Head piece?
• Creator's sine qua non
• Brainchild
• Theory
• Lightbulbs, in the comics
• It comes to a head
• Excuse, part 3
• Creative nugget
• Exclamation point?
• Inventor's "step one"
• Sneaking suspicion
• Bright thoughts
• Cortex activity