Related Clues:

• ''Let us know,'' initially
• Confirm, in a way
• Regrets, perhaps
• RSVP
• "Let us know," to an invitee
• Say something back
• Answer, shortly
• Heed an RSVP
• SASE contents, perhaps
• Invitation acronym
• Party thrower's request
• Say you will, or won't, be there
• Invitation ltrs.
• Brief answer?
• "Answer, please" (Abbr.)