BOSTON -- At last the Soviets have arrived, dressed in their best Western garb and bearing their finest glasnost. But there is one little secret they still want to keep from the folks back home: Mikhail Gorbachev talks with his wife.

When the Soviets released Gorbachev's interview with Tom Brokaw for home viewing, something was missing. It had nothing to do with ''Star Wars'' or human rights or Afghanistan. It had to do with Raisa.

Brokaw had asked Gorbachev, ''Do you go home in the evening and discuss with her national policies, political difficulties and so on in this country?'' Gorbachev replied, ''We discuss everything.''

But then Brokaw pressed the issue: ''Including Soviet affairs at the highest level?'' Gorbachev obliged, ''I think that I have answered your question in toto. We discuss everything.''

Well, Sergei, hand me the splicer.

The decision to edit out the last exchange was not, I am sure, made lightly. Raisa Gorbachev is the first truly visible first lady of the Soviet Union. With the Western role, she has gotten the Western perks: the high profile and the low blows.

In the Soviet Union, she is alternately criticized as a clotheshorse with a credit card and a petticoat behind the throne. Too frivolous and too powerful. According to rumors, she was the subject of an attack video within inner circles.

Does all this sound familiar? Nancy and Raisa could have a lot to talk about over their coffee.

In the Soviet Union, the image of women is rather like a multitiered cake: one layer of Russian traditionalism, a second of Marxist equality, covered with a frosting of romanticism.

The Lenins, Vladimir and Krupskaya, were about as close to partners as you find in modern Russian history. But Stalin, whose own wife committed suicide, was no friend of the Lenins' feminism.

Mrs. Khrushchev was little more than a huddled mass behind her man, one of the myriad political wives captioned only as ''spouse.'' As for Chernenko, nobody even knew whether he had a wife until she appeared at his funeral.

Today the modern Soviet woman is under pressures that may seem familiar to Americans. I once discussed ''the problem of women'' with the editor of the Soviet Workingwoman's Magazine. This young mother talked energetically about improving working conditions and sentimentally about encouraging readers to be more ''womanly'' at home.

Her magazine ran a contest to elicit the best ideas for changing the work place. And the prize for the contest was a miniature glass slipper. Cinderella with a five-year plan for Prince Charming?

Coming out of an atmosphere of mixed messages, Raisa Gorbachev gives hope to many Soviet women for the same reason she infuriates others: simply by portraying an intelligent and attractive woman. But in no way has she solved ''the problem of women.'' There or here.

A sociologist by training, at some point she too found it impossible to play both professor and politician's wife. Now she has replaced her old title with a new one: partner. Traveling partner for sure. But political partner?

The new woman of the Soviet Union is not unlike the next generation of American first ladies. From Liddy Dole to Hattie Babbitt, many of the candidates' wives now come with their own professions.

The American public also comes with lingering prejudices. Prejudices about how much power an unofficial partner should wield and how much independence she can show. We're not entirely comfortable with a first lady who leaves the White House every morning for her office. Nor do we want a copresident making decisions in the Oval Office.

This business of being a marital partner to president or premier is likely to remain as tricky as being fashionable without being vain, or being strong without being uppity.

Is it any wonder that the Soviets, newcomers to glasnost, haven't figured it out yet? This week, their reports on the summit may be open and freewheeling. But pillow talk remains the great Russian nyet-nyet.