While William P. Clark has just been installed in the top ranks of the White House staff, some presidential advisers are already pushing a second-stage shift that would mean the departure of presidential counselor Edwin Meese III--possibly to the post of attorney general.

All concerned vehemently deny knowledge of such a plan. Nonetheless, informed sources told The Washington Post that such a development is likely in view of the personalities involved and a feeling among some that Meese is miscast as a policy administrator.

The reshuffle is contingent on Clark's mastering his new role as President Reagan's national security adviser, building a competent organization at the National Security Council staff, and cementing a strong relationship with White House chief of staff James A. Baker III, these sources said. All that is likely to take from several months to a year.

But at that point a change will take place, they said, especially if a Supreme Court vacancy or some other such prize should open an opportunity for the president to shift William French Smith from the attorney generalship.

This scenario, according to sources with a long history as advisers to President Reagan, is advocated by Nancy Reagan, deputy chief of staff Michael K. Deaver and others with whom the president met during his most recent California vacation. It is not clear, however, whether the plan has been broached to Reagan.

Deaver, when informed of the substance of the report, termed it "preposterous." Sheila Tate, the First Lady's spokeswoman, said that Mrs. Reagan "does not involve herself in the personnel matters, or any matters, of the West Wing of the White House." Meese told The Post, "I think it's completely untrue." An aide to Smith said the attorney general had no such change in mind.

Nonetheless, both the original source and others privy to the discussions that led to Clark's replacing ousted national security adviser Richard V. Allen earlier this week insisted that the second step of the process would see the departure of Meese from the White House.

Their view reflected the belief, expressed with increasing openness in recent days by some subordinates of Meese, Baker and Deaver, that Meese would be better off in the law enforcement area, where he began his public career in California.

There have been reports that Meese coveted the attorney generalship before it was given to Smith, Reagan's personal lawyer, but Meese told The Post he could not credit reports that he might be shifted to the Justice Department.

"This is the first I've heard of it," he said. "The president and I have a relationship that if this were ever contemplated, I would know about it, and the same with Nancy and Mike."

Deaver said he was unaware of any desire on Meese's part to succeed Smith and said the notion that Meese would be sent there against his wishes "is a preposterous assumption. Bill Clark was brought over from the State Department to fill the Dick Allen vacancy, and there's nothing more beyond that."

In the face of those strong statements, The Post's sources said that as long ago as last summer and as recently as December, discussions before the president have surfaced the view that "the triumvirate" of Baker, Meese and Deaver "can't work" because "Ed wanders all over the lot and does nothing."

One person with access to the president said he personally had made the point to the president several times in the last six months, adding that, in his opinion, Reagan's experience with the work that reaches him through Meese as policy coordinator had provided evidence of tardiness and sloppiness in the operation.

This source also suggested that with Clark taking over as national security adviser, reporting directly to the president, Meese would find his remaining role as domestic policy counselor a secondary one. This would be particularly the case if, as some second-level White House staff members suggest, Meese's domestic policy deputy, Martin Anderson, is increasingly eclipsed in influence by members of Baker's staff.

The Post's sources raised two large cautionary notes, however. One is the lengthy period that Clark may need to establish himself as national security adviser and to rebuild what these sources described as a badly depleted staff in the Allen-era National Security Council.

The second is the uncertainty about Smith's tenure as attorney general. These sources said Reagan would not push Smith out, unless it was to a higher post, such as the Supreme Court; nor would he push Meese out, unless it was to a Cabinet position he would like, such as attorney general.