The railroad clerks union struck the Norfolk & Western Railway yesterday in the face of an impending contract settlement between the nation's railroads and four other rail unions.

A spokesman for the Virginia-based railroad one of the nation's largest and most profitable freight carriers, said the strike had "substantially" reduced operations on the 7,500-mile, 14-state system. But it was not expected to have any immediate economic effect.

The N&W failed to get a back-to-work order from a federal judge in Chicago. Its request for the temporary restraining order to send the more than 4,000 striking clerks back to work was rejected by U.S. District Court Judge Stanley J. Roszkowski.

The walkout at 6 a.m. by the Brotherbood of Railway and Airline Clerks came in the midst of complex negotiations for a national railway labor contract covering 11 separate unions, including BRAC, the second-largest rail union.

Four unions representing a majority of rail workers are reportedly on the verge of a settlement that would raise wages by 35 percent over the next three years. BRAC is not among them and is said to have problems with the proposal.

However, union spokesmen said the strike stemmed entirely from a longfestering dispute over union jurisdiction and job security within the N&W system and denied it was related directly to the nationwide contract talks.

They conceded, though, that the talks might have an effect on the bargaining by indicating militance on the part of BRAC members.

James Yoffie, BRAC's general chairman for N&W workers, was quoted by news service reports from Ronanoke as saying that N&W failed to negotiate in good faith ever since the union told the railway in October 1976, that it wanted to expand its jurisdiction and protect jobs threatened by technological advances.

A railroad spokesman said BRAC was trying to take over supervisory of other unions. "We could not legally negotiate over these jobs," the spokesman said.

The N&W has about 24,000 employes, about 90 percent of whom are unionized, according to company officials. Most of them respected BRAC's picket lines yesterday, officials said, and supervisory employes did what they could to keep the railroad running at what was described as "substantially reduced level of operations."

The N&W, which is based in Roanoke, is the nation's seventh-largest railroad and a profit leader in the industry, with lines connecting the Appalachian coalfields, Midwestern industrial centers and East Coast ports.

But most of its service areas are covered by other railroads, officials said. The N&W is a major mover of coal, which accounts for 40 percent of its revenue, but coal production has slacked off because of miners' summer vacations and because stockpiles have been built back up since last winter's long coal strike. Because the N&W is also a major [WORD ILLEGIBLE] of auto parts, the auto industry could be affected but only if the strike is protracted, officials said.

An official said the company, although rebuffed on the immediate back-to-work request on the immediate federal court in Chicago to schedule hearings on a request for an injunction, a process that could take several days.

In another later development, the Federal Mediation and Conciliation Service formally entered the stalled negotiations between the Postal Service and unions representing more than 500,000 postal employes. With only 10 days left before the three-year postal contract expires, the two sides are described as far apart on most major issues.

FMCS Director Wayne L. Horvitz met with both sides in what were described as "exploratory" talks yesterday and more meetings are planned today.

Carter administration inflation fighters have been bearing down on both the rail and postal talks in an effort to show the pace of wage increases, thus far with little encouragement from the bargainers.

The proposed 35 percent pay settlement for the rail unions considerably exceeds the administration's goal of 30 percent or less for rails over the next three years. And the postal unions are seeking a 14 percent increase for the first year of a two-year contract, more than double the 5.5 percent annual increase that the White House has said would be appropriate for postal workers.