Toronto's Carl Gunnarsson fanned on a scoring chance and Dainius Zubrus picked up the puck, rushing into the Maple Leafs' end. He stopped along the right half-boards and fired a pass to Clarkson alone in the slot.
The Devils winger one-timed a blistering shot between the pads of James Reimer and New Jersey snapped a four-game losing streak.
Clarkson also scored on a first-period power play, as did Ilya Kovalchuk for the Devils.
Martin Brodeur, the NHL's career leader in wins, broke a personal three-game skid, turning aside 29-of-31 shots.
Leading All-Star Game vote-getter Phil Kessel scored his 17th goal and Matt Frattin also scored for the Maple Leafs.
Reimer finished with 23 saves.