Related Clues:

• Head sets?
• They're sometimes wild
• Head starts?
• 'Any ___?'
• ''Don't get any funny ---!''
• Think tank output
• 'Gibraltar may be strong, but ___ are impregnable': Emerson
• Concepts
• Brain waves
• Lightbulbs, in the comics
• Bright thoughts
• Cortex activity
• Gray matter output
• Bean products?
• Suggestion box fill