Related Clues:

• Gasp, perhaps
• Change, chemically
• Horror-film sound
• Say "wow!", e.g.
• Get to work
• Respond
• Crank up
• Circus reaction
• Make a sound of shock
• 'Oh my!,' for one
• Make a face, say
• [Oh, my heavens!]
• Inhale in astonishment
• Word on a maze
• Take step one