AT LAST an honest night's movie about a hard day's work."Amber Waves," a two-hour drama from Time-Life Television, does what the best of TV movies, and few theatrical features, manage to do. It translates essay topics like "spiritual malaise" and "changing values" into intimate, heartfelt, human terms.

The film, probably TV's finest treatment of contemporary American life since "Friendly Fire," airs tonight on ABC (Channel 7) at 9. It is one of those rare entertainments about things that matter, and its terms are so human that it rarely sounds self-conscious, or even as preachy as the average "Lou Grant."

The role of Kansas in "Amber Waves" is played by Canada, where the picture was filmed during last fall's wheat harvest. At one point, a character arriving in what is supposed to be Kansas -- really Alberta -- says, as if to defend the illusion, "Wheat country looks the same in Canada."

Whatever the resemblance, the land we see in the film is not only beautiful, but welcome and fresh terrain for television. We get to forsake briefly the blacktops of L.A. for heartland plains and a sense of small-town ambiance that is totally unpatronizing. Essentially, "Amber Waves" could have been done as an intimate drama in a TV studio in the '50s, but for once location filming contributes to the effectiveness of a TV story. The land is a character as well as the setting; people's relationship to it is basic and resonant.

Dennis Weaver stars as a tough but fair-minded wheat harvester who hear, at the age of 49, the devastating pronouncement "malignant" from his doctor. He is dying of lung cancer, he learns, and he sees ways of life dying with him. Estranged from the son who nine years earlier fled to Canada to avoid fighting in Vietnam, the man clings desperately to values on which he was raised but which now seem imperiled or extinct.

The catalyst for the story is Kurt Russell (who played Elvis in the TV movie) as a male fashion model accustomed to the soft life and the Me Gospel, but stranded in Kansas after a pool-room brawl prematurely ends an assignment there. An unlikely alliance develops between the farmer and the playboy, and a less unlikely one evolves between the playboy and the farmer's daughter.

What the older man teaches the younger one, and vice versa, would sound awfully pat if put down on paper. Yet when writer Ken Trevey puts it down, and when the actors speak his lines, they sound authentic, honest and legitimately populist. Director Joseph Sargent helps Trevey bring out the points he wants to make without acrobatic, melodramatic maneuvering or gross over-simplification. The situation itself may appear contrived -- an outright set-up, pure and simple -- but the imagery is unusually rich for television and the narrative thoroughly engaging.

Weaver, though over-exposed on television -- and still so folksy as to make Charles Kuralt look like Noel Coward -- nevertheless brings imposing conviction to the role of harvester Bud Burkhardt and to his encyclicals on how life ought to be lived. "A man's word is his bond," he says. "I was raised on words like honor, and duty, and country," he tells his estranged son. "You can take a lot more than you thank you can," he informs the male model, who has temporarily joined the people who work for living with their hands and backs to produce our daily bread.

Russell, Weaver and the other performers give "Amber Waves" an unforced, immediate kind of pertinence. The word "malaise" never comes up, but that is essentially what the film concerns. It makes something concrete and specific, and very affecting, out of generalities. Like "Friendly Fire," it is able to summarize and express commonly shared anxieties and fears far more tellingly than a documentary on the mood of the nation ever could. Television still has tremendous power as a story-telling medium when the story-tellers know what they're doing and why they're doing it.

The family relationships are particularly well dramatized, with Mare Winningham brightness itself as Burkhardt's independent, impressionable adolescent daughter. She works with the young men on the harvesting machines, but on the day after she loses her virginity, she tells them with sweet understatement, "I don't feel much like one of the guys this morning."

It also helps that the estranged son, Greg (Grainger Hines), when he finally does show up, is not the saintly hippie figure one might have dreaded. He is something of a selfish brat, a reminder that not everybody who dodged the draft over Vietnam was necessarily a holy man fighting the good fight by avoiding the bad fight.

ABC Entertainment is circulating a memo that Philip Mandelker, executive producer of "Amber Waves," wrote -- "out of a deep personal sense of sadness, frustration and loss" -- to an ABC program executive on May 8, 1973, during the onset of the Watergate crisis. Mandelker wrote about "television's role" in helping people recover from the shock and discouragement of the time. What he said then sounds something like what the embattled Mr. Burkhardt is saying now:

"Not only do all the systems, values and morality which we were promised as children no longer seem appropriate in the world today, but I believe we have lost sight of what they were in the first place.

"However, there are certain values which one can only hope do indeed remain constant: love, honor and integrity. We are all seeking a sense of conduct, of purpose, of direction. At the moment there are no answers -- only questions."

Through all that may make it sound otherwise, "Amber Waves" is not treacly, grandiose or sanctimonioius. It ain't no lament, either. Nor do the Burkhardts lead a falsified "Waltons" life atop a mountain of wax Americana; people get hurt, a kid's dog is run over by a car, feelings are not always spared in fact are sometimes clobbered. And in the midst of all that organic grain and motherly nature, the family is outfitted with CB radios, microwave ovens and an SX-70 camera.

If it isn't the real world, it's more real than television usually gets. Weaver speaks of the "real stuff" that makes the difference between the frail and the hearty -- it's a lot like "true grit." In "Amber Waves," one can sense an ensemble of creative people trying to find that spark and make it shine and reaffirm its importance to what has become known as "the quality of life." It is a pleasure to join them in that search.