Related Clues:

• ''Why, the very ---!''
• It's all in your mind
• Bee Gees album title
• Inventor's need
• Hypothesis
• Brainstorming bit
• Cerebral creation
• Think tank output
• 'Gibraltar may be strong, but ___ are impregnable': Emerson
• Concepts
• Mental picture
• Mental flash
• 'What's the ___?!'
• Possible solution
• ...