Clue: X, in a love letter

Answer: KISS

Length: 4

---

Similar Clues:

• Who wrote "The only abnormality is the incapacity to love" (ANAISNIN with 8 letters)
• Alvy's love interest in a Woody Allen film (ANNIE with 5 letters)
• Letter inserts: Abbr. (ENCS with 4 letters)
• Love-letter addenda (EXES with 4 letters)
• 2001 album including the song "Love Don't Cost a Thing" (JLO with 3 letters)
• Letters to answer one's inviting letter? (RSVP with 4 letters)
• Today, I tried to put a self-effacing three-letter acronym inside each theme entry. Turns out it works in any order except the one I want. ___ (FML with 3 letters)
• Actress Martha who played Sinatra's love interest in "Some Came Running" (HYER with 4 letters)
• Catalog for polygamists on "Big Love" [The AV Club xword moves to a subscription model soon! Email bentausig@gmail.com for info] (JOYBOOK with 7 letters)
• Oft-abbreviated love-letter phrase (SEALEDWITHAKISS with 15 letters)