The Clark deal is for $14 million over four years. It was somewhat of a surprise after the Steelers also signed free-agent safety Will Allen to a three-year deal earlier Monday.
"Coach [Mike] Tomlin talked with me about being a nomad, a journeymen ... but if I finish my contract here, that's eight years in the same place, and that's an accomplishment," Clark said Tuesday. "I didn't want to leave. My neighbors didn't want me to leave. They didn't want to get new neighbors."
Allen's deal is worth $4.495 million with $975,000 to sign, a source told ESPN.com's John Clayton.
The team also signed wide receiver Arnaz Battle to a three-year deal, the team announced Monday. Battle's deal is worth $3.975 million with $975,000 to sign, a source told Clayton.
Randle El's deal was for three years as well.
The Steelers are also bringing in offensive tackle Jonathan Scott, who played the last two seasons in Buffalo under new Steelers offensive line coach Sean Kugler. Scott started eight games last season but wasn't given even the lowest tender offer to stay with the Bills.
After Washington released him last week, Randle El's first choice was to return to the franchise that he helped win a Super Bowl.
Bringing back Randle El and signing Battle suggests the Steelers may not be counting on former second-round draft pick Limas Sweed next season. He was taken off the active roster late last season for reasons not fully explained by the Steelers, who still haven't commented on the move.
Randle El figures to be the Steelers' No. 3 receiver, although he could be pressed for that job by second-year receiver Mike Wallace, who had six touchdowns among his 39 catches as a rookie.
"We talked about being the No. 3 receiver," Randle El said. "I'm focused on being the No. 3 receiver, and that's what I want to be. Certainly, If Hines or Santonio [Holmes] goes down, of course, being [lined up] outside. ... It's a great situation. I have some history here."
Despite being a disappointment in Washington, Randle El caught at least 50 passes each of the last three seasons; the most receptions he had with Pittsburgh were 47 as a rookie in 2002.
Both Allen and Battle have links to the Steelers' coaching staff. Allen spent the past six seasons with the Tampa Bay Buccaneers, where he once worked with current Steelers head coach Mike Tomlin. And former San Francisco 49ers special teams coach Al Everett, now Pittsburgh's special teams coach, recommended Battle to Tomlin.
Battle is expected to help the Steelers as a backup wide receiver and offer help on special teams. He started 38 games for the 49ers from 2005 through 2007 and caught 141 passes during that span.
Allen, who lost his starting job in Tampa Bay, and Battle, whose playing time at wide receiver was reduced in San Francisco, should upgrade the Steelers' deficient special teams. Their four kickoff return touchdowns allowed last season led the NFL.
"That's what I'm good at, that's what they saw in me," Allen said. "I'm a good safety and a good special teams player."
Information from ESPN NFL Insider Adam Schefter, ESPN.com senior NFL writer John Clayton and The Associated Press was used in this report.