Possible Clues:

• One after cuts about to make comeback
• The letter I posted contains the answer
• I have letters again to take round, requiring an answer
• Answer I start to provoke inside versatile store
• Quick reply in letter I posted
• Old Stone in mellow comeback
• Quickly return mail with Royal Institution heading and seal for envelope
• Retaliatory tactic
• (In fencing) a quick return thrust
• Sally's grave letters -- love the way she finishes