Possible Clues:

• Defiant way to respond to insults
• You hit me, I hit you
• Retaliation? Be it on Cockney's head!
• As the only difference, I must come in for a bit of retaliation
• Mechanical trade
• Payback time -- gift of poor Stuart's oddly mislaid
• In equal measure
• Retaliation for an injury - almost equal
• Report of 19 shoddy items? Retaliation called for
• Equivalent retaliation