Related Clues:

• Come back
• It's much requested
• Don't just sit there
• Jerk one's knee, e.g.
• Don't just stand there
• Strike back
• Answer
• Bounce back
• Respond to a stimulus
• E-mail program button
• Show surprise
• Respond to stimuli
• Jump at a noise, e.g.
• Show one's emotions
• Strike back, say