Just as she did in “Easy A,” Patricia Clarkson will add a veteran presence to the youthful ensemble of Zal Batmanglij’s eco-terrorist thriller “The East.”Sundance breakout Brit Marling stars an employee of a private contracting firm who goes undercover to infiltrate a mysterious anarchist org known only as The East. Alexander Skarsgard co-stars as the leader of The East, while Ellen Page and Toby Kebbell play members of the group. Clarkson is set to play Marling’s boss, who’s every bit as tough and unyielding as her best agent. Marling and Batmanglij wrote the Fox Searchlight film, which is being produced by Ridley and Tony Scott’s banner banner, whose prexy Michael Costigan will produce with Jocelyn Hayes Simpson and Marling. Production starts Nov. 1. Clarkson, who recently appeared in the studio pics “Friends With Benefits” and “One Day,” is coming off an arc on NBC’s hit sitcom “Parks and Recreation,” in which she plays Tammy One, the first ex-wife of Ron Swanson (Nick Offerman). Clarkson is repped by CAA and Anonymous Content.