Related Clues:

• Waiting in the wings
• Aware, with 'in'
• Attuned
• Nervous, with 'up'
• Tensed, with 'up'
• Atwitter, with 'up'
• Excited, with 'up'
• Worked (up)
• Tense (with ''up'')
• Like a piano
• Tense (with "up")
• -- up (excited)
• Ready when needed
• Typed in
• Entered data into a computer