In its first move as a publicly traded company, Clipper Realty is buying an 11-story Brooklyn Heights rental building from the Jehovah’s Witnesses for $87.5 million, the firm told The Real Deal. The David Bistricer-led real estate investment trust entered into an agreement to buy 107 Columbia Heights for $569 per square foot. The Witnesses put the 154,000-square-foot building on the market in April.