Heat broiler, with rack set 4 inches from heat. On a broilerproof rimmed baking sheet, rub pork with 1 tablespoon oil; generously season with salt and pepper. Broil, until pork registers 145 degrees on an instant-read thermometer, 12 to 14 minutes. Transfer to a plate, cover loosely with aluminum foil, and let rest, 10 minutes (temperature will rise about 5 degrees as it sits).
Meanwhile, in a large skillet, heat remaining tablespoon oil over medium. Add leeks and fennel seeds; cook, stirring occaionally, until leeks are tender, about 6 minutes. Add apples, and cook, tossing, until just beginning to soften, 3 to 4 minutes. Remove from heat; stir in honey and vinegar, and season with salt and pepper. Thinly slice pork, and serve with apples and leeks.