World Bank President-elect A. W. (Tom) Clausen said in an interview here today that he is "attracted to the idea" of a new energy affiliate for the bank, which would be responsible for helping to finance energy development in the Third World.

The Reagan administration officially notified the World Bank at the beginning of its term that for the moment it could not support the affiliate proposal, pending completion later this year of a study of all U.S. commitments to multilateral lending institutions.

Clausen, who succeeds Robert S. McNamara as World Bank president on July 1, recently resigned as chief executive officer of Bank of America, the holding company for the nation's largest bank. He was confirmed for the World Bank post on the nomination of President Carter just before the 1980 election, with the approval of Republican presidential candidate Ronald Reagan.

Here for the annual meeting of the international monetary conference of the American Bankers Association, Clausen said that obtaining a greater supply of energy is the "main problem we face" and that a World Bank affiliate concentrating on energy would have many favorable aspects.

The Reagan administration's attitude toward the energy affiliate -- endorsed by the United States and others at the Venice summit in 1980 -- became one of the contentious points between the United States and the less-developed world.

"I'm gung-ho for energy," Clausen said, "and I don't intend to lose the war. I will very carefully analyze the arguments raised against an energy affiliate, and if there is some other way to do it, okay. But the main idea is to get the energy."

He said the Reagan administration is also anxious for energy development but that the reported opposition to the World Bank affiliate had "unfortunately been misinterpreted."

Clausen implied that he was seeking to get the administration to change its mind. But his remark about not losing "the war" was intended to convey his own flexibility of approach, provided that the main goal of boosting energy production was achieved.

He said the main reason that he likes the affiliate idea is that it is the easiest approach to "breaking away" from the rigidly constructive "gearing ratio" of the World Bank itself. Under the gearing ratio, the bank can lend only one dollar for each dollar of bank capital. Robert McNamara proposed at last year's annual bank meeting that the ratio be liberalized to 2 to 1. "I just came from a bank where we have had gearing ratios as high as 28 to 1," Clausen said, adding that he has nothing like that in mind for the World Bank, but that "no World Bank loan is ever going to be defaulted."