Related Clues:

• Embryo of an invention
• It's in your head
• Sometimes it's for the money
• Clever thought
• Mind matter
• Creative spark
• Just a thought
• Start of a long distance call
• Washington is on it
• Plan of action
• It's heard before a liftoff
• 'A Chorus Line' number
• See 34-Down
• Lightbulb, in toons
• Formula ___