An era is truly over for Washingtonians who have been reading Diana McLellan's whimsical gossip for the past 10 years. At the end of September she will sign off on her column and on Oct. 1 will become Washington editor at Washingtonian magazine. McLellan, whose "Ear" column was a major success for six years at the Washington Star, wrote it for one year at The Washington Post after the Star died. Her three-year contract with The Washington Times ends in September.

When asked why she was ending her successful column, McLellan said she remembered that Igor Cassini, who wrote a column under the byline Cholly Knickerbocker for the old New York Journal American, said you go nuts after five years of writing a gossip column. "As for me, I've loved doing it, but 10 years was long enough," she added. McLellan says she will also be writing a novel whose central character just happens to be a gossip columnist.

Times executive editor Woody West described McLellan as "inimitable," but added that she will write occasionally for his paper. At the Washingtonian, McLellan will write a monthly humor column and a monthly feature. Washingtonian editor Jack Limpert said yesterday that McLellan "will be writing about money, power, sex, restaurants and real estate -- all the things we've been neglecting all these years."