The Redskins remedied a glaring defensive problem yesterday by obtaining 290-pound lineman Wilbur Young from the San Diego Chargers for their most promising young veteran offensive lineman, guard Jeff Williams, who had fallen out of favor with the current coaching staff.

Young, 6-foot-6 and an 11-year veteran pass rusher from William Penn College, is expected to challenge Perry Brooks for a starting tackle job. He also will contend for Coy Bacon's end position, where Mat Mendenhall, last year's No. 2 draft choice, has been projected as this season's starter.

General Manager Bobby Beathard, who made his seventh trade since early April, had another major concern yesterday. He is scrambling to sign quarterback Tom Flick, a fourth-round pick from the University of Washington, who is being heavily courted by British Columbia of the Canadian Football League.

Flick told the Redskins he would make a decision today. The CLF club is 150 miles from Flick's home in Seattle. Beathard, who says he believes Flick will sign with the Redskins, did not expect British Columbia to mount such a strong challenge for Flick, who, should he sign, probably will be the Redskins' backup quarterback this season.

The trading of Williams, a starter the last two seasons when he emerged as the team's best offensive lineman, undoubtedly will serve as a warning to other players that Coach Joe Gibbs won't tolerate his athletes being out of shape or missing minicamps.

Williams passed up Gibbs' first minicamp in April. Though the camp was voluntary, the coaching staff was upset by his absence. He also reported in poor physical condition to the mandatory camp May 7-9 and sprained an ankle the first day.

"We weren't happy with Jeff's physical condition but that wasn't the reason he was traded," Beathard said. "We had an opportunity to obtain help for our defensive line and we took it. Wilbur is huge and a fine pass rusher. We didn't want to let Jeff go, but with the way our young players looked at the minicamp, we feel the offensive line now has depth enough to make a trade like this."

With Williams gone, either Melvin Jones, the second-year man from Houston who spent last season on the injured reserve list, or Gary Sayre, this year's fifth-round pick from Cameron State who had an impressive minicamp, emerge as the top candidates to start.

Veteran Fred Dean, a starter at tackle in 1980, has been moved to left guard and is expected to dislodge veteran Ron Saul. Another rookie, center Russ Grimm, also can play guard and could move over if he can't beat out Dan Peiffer or Bob Kuziel at center.

Williams, 26, will be reunited in San Diego, with his former coach, Jack Pardee, now the Chargers' defensive coordinator. Pardee, who has long regarded Williams as a future all-pro, recommended the trade. The Chargers, worried about the physical condition of Russ Washington, are expected to try Williams at tackle. Williams originally came to the Redskins in 1978 in a deal with Los Angeles involving Eddie Brown.

This is the first of Beathard's recent deals that directly involved help for the Redskins' undermanned defense.

Before obtaining Young, who played behind two Pro Bowl tackles last year after recording 14 sacks in 1979 as a tackle, Washington had just two experienced players at that spot, Dave Butz and Brooks, who couldn't hold down a starting job in 1980. While their depth at end is better, the Redskins still haven't signed Bacon -- but expect to before training camp -- and Mendenhall is inexperienced and unproven.

Young, 32, was unhappy with his lack of playing time last year and had only two sacks in 12 games. He was named the club's most valuable defensive player in 1980, when Louie Kelcher was sidelined with a knee injury. He had asked to be traded.

He was picked by Kansas City in the second round of the 1971 draft. He has 60 1/2 career sacks and has started seven seasons.