Possible Clues:

• Keep at bird first in retaliation
• Retaliation? Be it on Cockney's head!
• 'Measure for Measure' in full East-ender's headgear?
• In kind
• Computing pro volunteers to cut off alcohol in revenge
• In annoyance, return bird, plump, having nothing right to eat
• Balanced reaction involving change of heart
• Defiant way to respond to insults
• Appropriate retaliation
• Mechanical trade