For a half-dozen years, when she was playing down-to-earth cop Mary Beth Lacey, Tyne Daly would arise each day at 4:30 a.m. to go off and face her "perp" of the week, working at a frenzied pace with little rehearsal - and somehow managing to bag the bad guy, the perpetrator, by the end of each episode of the much-admired "Cagney and Lacey."

Not anymore. "Cagney and Lacey" has gone to syndication heaven, and Daly is tackling another heavenly performance challenge: playing Mama Rose in the 30th anniversary revival of "Gypsy."So, Tyne, how big a risk is it to make your Broadway musical debut in a part created with Ethel Merman in mind, a part also played with flamboyance by Rosalind Russell and Angela Lansbury?

"Big!" she booms with Mary Beth Lacey's exuberant laugh.

"Gypsy's" long road to Broadway began May 9 at Miami Beach's Jackie Gleason Theater of the Performing Arts. During the show's six months on the road, Daly will endure separations from her longtime husband, actor-director Georg Stanford Brown, and their daughters Alisabeth, 21, Kathryne Dora, 18, and Alyxandra Beatris, 3.

"This is the actor's life," she said during a recent stop in Miami to promote the show. "Georg and I have been married a long time. He was gone for eight months the second year Zannie was alive, and she thought he lived in the airport. This is my kind of normalcy."

What fans of Mary Beth Lacey may not realize is that Daly is an accomplished and experienced stage actress. Daughter of the late James Daly, who had a seven-year run on TV's "Medical Center," Daly began acting professionally in high school.

Daly made her off-Broadway debut in "The Butter and Egg Man." Then, when Brown's movie work took them to Los Angeles, she began amassing TV credits - "The Virginian," "The Entertainer," "The Women's Room," four episodes of "The Rookies" and, of course, "Cagney and Lacey."

But she also kept working on stage in such plays as "Ashes" and "The Three Sisters" at the Mark Taper Forum in L.A. and Bertolt Brecht's "Caucasian Chalk Circle" in Denver. She won a best actress award for playing the "Shirley Booth role" in William Inge's "Come Back, Little Sheba" at the Los Angeles Theatre Center in 1987.

Though she does have a Mermanesque belt to her voice, Daly's not worried about comparisons to the inimitable Ethel Merman. She's more concerned about tackling a role she considers one of theater's greatest for women and making it her own.

Her director, Arthur Laurents, is enthusiastic about what he thinks Daly is bringing to the immensely successful musical for which he wrote the book in 1959.

"I love the show, it's a wonderful show," Laurents said during a rehearsal break in New York. "I don't care about anniversaries, just as I don't believe in doing revivals the same way as the original. You do it from the viewpoint of the time you're in and the people you're working with.

Daly believes that "Gypsy" is far more than the musical biography of striptease queen Gypsy Rose Lee, her actress-sister June Havoc and their Mama Rose - who is, to put it mildly, the quintessential stage mother.

"This play has Greek proportions to it," she said. "It's got emotions, mother-daughter conflict. It's about ambition. It's got romantic interest. And it's musical theater, which is an American art form . . .

"I think you could play it without the songs and dances, almost, and have it be there."