LOS ANGELES (AP) - John Lennon thought Eric Clapton had promise. In fact, he offered to help Clapton develop his talent in a letter dated September 29, 1971. That letter is for sale by the auction house Profiles in History, and it's expected to bring in at least $20,000. In the letter, Lennon tells Clapton, "I know I can bring out something great -- in fact greater in you that had been so far evident in your music." Lennon says he knows it'll happen if and when they get together. The auction is December 18 in Los Angeles.