You are the ambassador of an African country, and you are under instructions to answer a question of supreme symbolic and practical significance to all of black Africa (and South Africa as well): what is the policy of the U.S. government on Angola?

Hostile, is the short answer, if you are talking to the State Department or the White House. The Reagan administration's policy is to continue to treat this former Portuguese colony as a Marxist pariah, infested by some 20,000 Cuban troops; a Soviet client unfit for the diplomatic recognition accorded it by the United Nations and almost all of Europe and Africa.

In this spirit, the Reagan administration has high on its list of foreign policy objectives in Congress the repeal of the 1976 amendment authored by the former Democratic senator from Iowa, Dick Clark. It was designed to shut down covert (CIA) support for the guerrilla forces of the National Union for the Total Independence of Angola (UNITA).

Secretary of State Alexander Haig calls the repeal proposal a "matter of principle" and "not a reflection," as he put it to me not long ago, "of an appetite to get in there and muck around." But it was Henry Kissinger's appetite in the Ford administration for a $ 25 million program of clandestine support of the UNITA forces that gave rise to the Clark amendment. Acute memories of the Vietnam debacle and fresh disclosures of CIA excesses right about that time had given almost any American overseas "intervention" a bad name.

While that dark disenchantment may have lightened a bit with the passage of time, there remains considerable opposition to striking the Clark amendment from the books. So when our hypothetical African ambassador touches base with the legislative branch, in further search of a rounded view of the U.S. government's policy on Angola, what he discovers is a critical absence of trust and common purpose between Congress and the executive branch.

The case of Angola is not unique. But it is a particularly striking example of how the projection of a consistent and coherent American policy can get confounded when Congress, either out of justified mistrust or a simple compulsion to meddle, insists on elbowing into the act.

Looking back to 1975, when the Soviets first moved into Angola with their Cuban surrogates, Sen. Daniel Patrick Moynihan (D-N.Y.) insists that both the Kissinger plan and the Clark amendment were the wrong ways to go about it. He was then the U.S. ambassador to the United Nations, and what he remembers is a monumental missed opportunity to rally black Africa against Soviet (which is to say "European") neocolonialism.

"The Africans were scared," he recalls, and the United States could have scored big by taking the Angolan issue to the U.N. General Assembly as a "huge ideological issue." This not having been done, he argues, the Africans were left "with no grounds on which they themselves could resist" the Soviet intervention in Angola.

In any case, Kissinger favored the covert route and got blocked, and now the problem lies in the implications of untying the president's hands: the signal this would send to black Africa, the suspicions it would raise about the administration's real intentions. Those who would hang on to the Clark amendment argue that UNITA is solidly backed by South Africa, with which the Reagan administration has been striking up an ever-tightening alliance.

Freeing the president of the Clark amendment's constraints would be at least an indirect gesture of support for the guerrillas in Angola. And this could upset the careful balance needed for the U.S. role in seeking a solution to the future status of neighboring Namibia. It would also, the argument goes, only serve to tighten the Angolan government's Soviet/Cuban connection.

Perhaps. But the most valid expression of American foreign policy ought to lie not in inadvertent congressional signal-sending, but in the performance of the executive branch. The administration's point of principle is sound. What is more, for Congress to retain a selective hold on CIA covert activity in Angola alone would seem to be a vote of no confidence in its own reformed procedures for CIA oversight.

Even though the Senate has voted to repeal the Clark amendment, a technical hang-up probably will keep the House (which leans the other way) from acting before the Christmas recess. And so, for a full, rounded view of the U.S. government's policy on Angola, our African ambassador is probably going to have to tell his government to wait 'til next year.