When Lynda Clendenning first began work 12 years ago as a clerk at a University of Maryland library, taking maternity leave was a risk, not a right, because pregnant women were pressured, she said, either to resign or to hurry back to work.

Library clerks parked their cars a 15- or 20-minute walk from the library, no matter how much seniority they had, while librarians automatically parked next door. And while a labor union did exist, most workers, including Clendenning, were afraid to join, believe they had no protection if a supervisor branded them troublemakers and pressured them to resign.

"These things may seem very minor, but it was the whole atmosphere then," Clendenning said. "It was very paternalistic. We were treated like children."

These days, Clendenning, 36, is still a University of Maryland library clerk, but she is also president of the 600-member American Federation of State County and Municipal Employees Local 1072. Having worked to change many of the conditions she found years ago, she has moved on to a new struggle for higher pay. That struggle, labor experts say, could involve one of the most important and far-reaching labor issues of the 1980s.

The issue is known as "comparable worth," and it refers to the effort by working women to upgrade pay in traditionally female-dominated jobs. The subject was featured, along with Clendenning, in last Sunday night's episode of the "America Works" series on WDCA-TV (Channel 20).

Produced by the AFL-CIO in an effort to improve labor's image, the $2 million, 12-part series discusses issues of interest to labor and the general public. The Sunday segment, the third in the series, was aimed at 45 million American women who work full time outside the home. It profiled the successful effort by Clendenning and other activists last spring to pressure a high-level task force appointed by Gov. Harry Hughes into considering comparable worth in its review of a new pay scale for the state's 64,000 employes.

The struggle for "comparable worth" adjusted pay is considered the second stage in the fight for higher pay that working women have waged since the Equal Pay Act of 1963 guaranteed women the basic right to equal salaries for equal work.

Comparable worth goes a step further. Comparable worth advocates say women need not be doing exactly the same jobs as men to deserve equal or higher pay because the value of their contribution is often worth as much when viewed by some objective measure.

"When people say clerical work," Clendenning said, "the other thing they usually say is 'routine.' Well, we have secretaries planning international trips, dealing with embassies around the world. We have secretaries formulating budgets of over $1 million. . . . There's nothing routine about that."

Clendenning's interest in the issue arose from her work with the AFSCME local that she has headed since 1976. The local represents support staff at the University of Maryland's College Park campus, including secretaries, clerks and plant workers.

In Clendenning's own job in the library, she saw how the work of clerks or library technicians began to change with automation, which gave clerks responsibility for understanding and helping library users negotiate the three different computer systems used by the university. Clerks also became more responsible for cataloging.

She began to believe that her employer, the University of Maryland, did not fully appreciate or compensate the work her colleagues performed. Clendenning, who has a bachelor's degree and has completed half the work toward a master's degree, is paid $15,500 a year.

Comparable worth was an issue that came to the attention of feminists and labor organizers in the mid-1970s when they began to notice that the work force was--and still is--largely segregated by sex, and women still make about 59 cents on the average for every dollar earned by a man--the same proportion of 20 years ago.

Comparable worth supporters say they believe many women in female-dominated careers are undervalued and underpaid--not because the jobs require less skill, effort and responsibility than work performed most often by men, but because "women's work" is held in low regard.

Some employers also assume men are breadwinners and thus in need of higher wages than women.

Supporters of comparable pay say women are forced to compete against each other for the lower paying jobs because of discrimination, keeping their own wages in check. And they say the movement is especially important now that women are the sole support of one in six American families.

Efforts to advance the issue in court and in government have had mixed results, said Susan Deller Ross, director of Georgetown Law Center's Sex Discrimination Clinic.

In a 1977 case, secretarial workers at the University of Iowa sued because a university evaluation rated their jobs equal to those of predominantly male plant workers, but the men were paid more anyway. The women lost. But in August 1981, the Supreme Court ruled that a similar argument advanced by female corrections workers in Washington state could be used as grounds for a lawsuit over pay there.

A push for comparable worth can clash with other social problems and rights, however. In one case, female corrections workers earned less than men, in part because they were restricted to certain areas of the jail--an effort to protect the privacy rights of male inmates. And many governments and businesses are reluctant to undertake an effort that could cost millions.

Despite the obstacles, Clendenning decided to pursue the issue when she learned of a high-level commission appointed by Hughes to review compensation plans for state workers. A consultant's report delivered last September did not take comparable worth into account, and it called for most secretarial work to be in one category.

Clendenning's union organized a workshop for labor leaders throughout the state and also held hearings on campus to which public officials were invited. Members of the local testified before the governor's commission, and Clendenning met with Theodore E. Thornton Sr., the secretary of personnel. As a result, Hughes authorized another study taking comparable worth into account. The new study is expected to cost $50,000 to $70,000.

Clendenning said the concept has wide social benefits, including allowing more workers to believe their labor is worthwhile. "People used to be apologetic about what they did. I was. I used to say, 'I'm just a technician,' " she said. "Now I say, 'I'm a technician.' "