At the age of 80 and still going strong as a corporate lawyer and political sage, Clark Clifford is the quintessential insider in what people in Washington have come to call Power Town.

He came here from Missouri during World War II before there was a Beltway to be inside of. He was Lyndon Johnson's secretary of defense in the darkest Vietnam War days, so he knows a failed foreign policy when he sees one and also how to go about trying to set it right. He was chairman of a special presidential board charged with continuing oversight of the very kind of intelligence operations that got so sickeningly out of responsible government control and gave us what is so inadequately identified as the Iran-contra affair.

But more important he has theclearest sense of anybody around of what President Harry Truman had in mind when he persuaded Congress to pass the National Security Act of 1947. For it was to Clifford, the young White House aide, that Truman turned to with instructions to draft the law that produced the National Security Council and the Central Intelligence Agency.

This law gave us the rules of engagement in foreign-policy making that have served us well when they have been followed over the last 40 years and disastrously when they have been flouted or lawlessly abused.

With this general thought in mind, I asked Clifford how far he thought we have strayed from the original spirit and intent in those formative, perilous and richly productive years of American foreign policy -- and what's now needed to get us back on track. This is the first of two dispatches on the findings and recommendations of the ''Clifford Committee'' -- a one-man, institutional memory bank whose gentle manner and mellifluous voice, with its rolling cadences that sink to a whisper for emphasis, belie his evident outrage, his scorn and his dismay.

He doubts we will ever get the facts: ''There was a gun case of smoking pistols, but they all went into the shredding machine.'' Still, drawing on the available evidence, he knows more than enough to be clear about what he thinks of the Iran-contra debacle:

''We read of events taking place that surpass any nightmare we have ever had -- unbelievable acts that bore no resemblance whatsoever to the functions of the NSC and the CIA . . . a secret government operating in a democracy. . . . I don't think our forefathers had any concept of anything like that taking place. I know I had no thought at any time of such an organization taking place. . . . This operation constituted the grossest kind of violation of the tenets of our government.''

A harsh indictment, perhaps, but understandably so when you consider Clifford's perspective. It begins in the mid-1940s with the remarkable relationship he had with two principal players of those times: Dean Acheson and James Forrestal. Out of their regular meetings and close friendship came ''the real genesis of having somebody at the White House who was liaison for defense and state,'' Clifford believes.

The establishment of the NSC included no statutory provision for a national security adviser to the president or even an NSC staff. Clifford, in his capacity as White House counsel, played that role -- with one assistant. The NSC consisted of the president, the vice president, the secretaries of state and defense as full members. It was to operate strictly as a deliberative ''advisory group.'' The voice lowers abruptly: ''I remember that very clearly.''

Truman had told him he wanted only ''recommendations'' from the NSC; he would make the decisions -- ''everybody understood that very well.''

For its part, the CIA was intended to be nothing more than a ''repository'' of government-wide intelligence gathering: ''At no time was it meant to be a covert agency. That was not in Truman's mind at all.''

The argument (or alibi) is now made that those were easier, less complicated times; that the U.S. government is much larger today; that the CIA was almost forced by the nature of the deadly game into covert operations; and that by no means did the system always work, as witness the Bay of Pigs or the entanglement in Vietnam.

But Clifford answers that the basic relationships worked in a more or less civilized, constructive way throughout the Eisenhower, Kennedy and Johnson years. The skewing of the relationship between the White House and State began with Nixon and served, as Clifford sees it, as the precedent for the raw White House-State relationship in the Carter days.

That the old-fashioned ways fell out of fashion, however, makes them no less valuable as a point of departure for anyone interested in how to go about restoring law and order to foreign-policy making. For it is nonsense to say that the good old days that Clifford was talking about were exactly carefree times. There was a cold war on, a Berlin blockade, a serious communist threat to a shattered, destitute Western Europe, a Korean war. The Reagan presidency has been taxed by nothing even remotely as challenging as the Marshall Plan or the Cuban missile crisis.

Clifford is under no illusions that the reel can be run backward or that the old spirit of the immediate postwar years can be recaptured or that Congress can write a law that a president cannot find a secret way to break. But Clifford does have clear ideas about what could be done to make that more difficult