The new dukes-up, don't-mess-with-me, expect-anything foreign policy of the Reagan administration had to throw in the towel in one round of the foreign aid fight in the House.

Big Ed Derwinski of Illinois, who as ranking Republican on the Foreign Affairs Committee is the president's handler, stood up unexpectedly and announced that he had decided to withdraw an amendment that would have unleashed the CIA in Angola where, to the outrage of the right, 20,000 Cuban troops keep order for a Marxist regime.

The Democrats were charmed, especially young Howard Wolpe (D-Mich.), chairman of the Africa subcommittee who was not at all sure he had the votes to stop repeal of the five-year-old Clark Amendment, which specifically forbids the agency to engage in any covert or overt activity in Angola.

But Derwinski had figured out that victory on the repeal might cost him the entire bill. Naturally, as a Republican, he is unaccustomed to leading the charge for what Republicans have always called "money down a rathole."

They have, as instructed by the president and the secretary of state, tried to rethink it as an investment in "national security," but it goes against the grain. The Democrats, knowing this, have threatened to vote against the bill on grounds that amendments such as the Clark repeal, not to mention military aid to Pakistan and removal of restrictions on arms sales to Argentina, make it an outreach program for dictators. They would be satisfied with a "continuing resolution" that would eliminate these obnoxious provisions, all of which are in the bill passed by the Senate.

Just after Derwinski sent the amendment back to its corner, Wolpe left the floor for a meeting with Jonas Savimbi, leader of the Union for the Total Independence of Angola (UNITA), the Angolan rebel faction. Savimbi had U.S. support in the Angolan civil war until the Clark Amendment cut it off.

Savimbi, who requested the meeting, has been in town for a week, pleading for understanding of his continued resistance to the Marxist government in Angola. He is a hero to right-wing Republicans and an exception to Ronald Reagan's deep antipathy to guerrillas.

So much does Reagan esteem this "freedom fighter" that he proposed to invite Savimbi to the White House last spring. The move was blocked after the personal intervention of a vice president of Gulf Oil Corp., which like several other U.S. conglomerates, including Chase Manhattan and International Telephone & Telegraph, enjoys a most profitable and cordial working relationship with the Marxist regime. That government is much more interested in developing the great natural resources of the country than in ideological niceties.

Savimbi, a huge, handsome, bearded figure in impeccable fatigues, finally visited under private auspices, to be lionized by conservative organizations such as Freedom House and the American Enterprise Institute. There is some question about how much of the countryside he controls but none about his charisma.

He insisted that it was "just a coincidence" that he arrived four days before the Clark Amendment was to hit the floor.

When Wolpe told him it had been shelved, Savimbi said it was of no consequence to him. He said he not only wants Cubans out of Angola but also South Africans, who have aided him occasionally. He wants to talk only of Angolans.

In his literature, and in his discussions with such hawkish groups as the House Armed Services Committee, Savimbi has stressed the strongly anti-Soviet nature of his guerrilla operations. Wolpe taxed him about ideological differences with Angola's ruling Popular Movement for the Liberation of Angola (MPLA). Savimbi's tory fans on Capitol Hill might have been saddened to hear him say that, while he is indeed anti-Soviet and pro-western, he favors socialism, a form modeled on Chinese and Tanzanian collective villages.

What he wants most, he emphasized, is a solution in South Africa. He puts that above his own claims. A Namibian settlement would remove the MPLA's rationalization that the Cuban presence is imperative to counter South African aggressions. He told one right-wing group that "if the Cubans leave, the MPLA would have no basis whatsoever to be in power." He assured Wolpe, however, that he seeks political reconciliation with the MPLA.

Rather surprisingly, Savimbi said such a reconciliation should not be undertaken under U.S. auspices. He believes that other African nations should be the mediators. Wolpe found him "impressive."

What the afternoon's work comes down to is that the administration may inadvertently have improved the chances for peace in Angola and South Africa. Who knows, they may have learned something about the wisdom of retreat. In a week that brought a rejection of their most basic domestic doctrine--that budget deficits are the work of the devil--they may be ready to consider the startling notion that discretion is sometimes the better part of valor in foreign policy.