Two-time Wimbledon tennis champion Boris Becker has been dropped as a good-will ambassador for UNICEF, the United Nations Children's Fund, after refusing to pledge not to play in South Africa. Becker joined the UNICEF roster last year and donated substantial sums to the agency, which provides food and health services to mothers and children in poor countries.

Becker has refused to play in South Africa since 1984 and has publicly condemned apartheid. Nevertheless, the U.N. agency said it took the action because Becker had not made a categorical declaration that he would not compete in that country while apartheid reigns. At the same time, UNICEF named British filmmaker Richard Attenborough as a good-will ambassador. His new film, "Cry Freedom," which is about apartheid fighter Steve Biko, is being released this weekend. Out and About Soviet Foreign Minister Eduard Shevardnadze's surprise visit to Washington tomorrow has disrupted some social plans at the Soviet Embassy here. This weekend is the annual running of the Washington, D.C., International horse race at Laurel, and for the first time in a number of years, two of the horses entered are from the Soviet Union. Among a host of scheduled events was a cocktail reception at the embassy tomorrow, to be followed by dinner at the French Embassy. With Shevardnadze coming, the local Soviets felt they had to shift affairs of state back to the front burner, so, although the French dinner is still on, the Soviet reception has been canceled ...

Playboy magazine is coming to town next week to photograph "The Women of Washington" for undraped display in the magazine later during the 1988 election campaign. Veteran photographer David Chan will be at the Four Seasons Hotel Nov. 4 to screen applicants. He was here in 1976 for a similar pictorial titled "Girls of Washington." Why Washington now? Jeff Cohen, Playboy's managing photo editor, said, "Washington has become a glamor capital ... The city is strongly identified with beautiful, intelligent women with interesting jobs. While the focus of the world is on the election of a new president, we have decided to spotlight the best and the brightest women in the political capital of the world." Unfortunately, if some of those best and brightest women with interesting jobs are photographed in something less than full garb, they may very well be looking for new jobs soon afterward. Politics and Playboy aren't always perfect bedfellows ...

Actor Matthew Broderick, who hasn't been seen around much since his Aug. 5 car accident in Northern Ireland in which two women were killed, has a scheduled court date there Feb. 15. He has been charged with reckless driving. Still having some difficulty getting around because of a shattered leg he suffered in the wreck, Broderick is undergoing daily therapy. This week he made his first public appearance, with a reading from a series of newly discovered plays by Ben Franklin at a benefit for the Writers Theater in New York ...

Dawn Steel, one of Hollywood's most successful executives, has been named president of Columbia Pictures, succeeding David Puttnam, who stepped down a month ago. The 41-year-old Steel, who has come a long way from her beginnings as a receptionist, had been president of production at Paramount Pictures, where she was responsible for such box office smashes as "Footloose," "Top Gun," "The Untouchables" and the studio's latest money maker, "Fatal Attraction" ...