Preheat oven to 325°F. In a small bowl, combine the brown sugar, marmalade and mustard; set aside. Score the surface of the ham, making diamond shapes 1/2 in. deep; insert a whole clove in the center of each diamond.
Place ham cut side down on a rack in a shallow roasting pan. Bake, uncovered, until a thermometer reads 130°, about 2 hours.
Brush ham with some of the glaze. Bake until a thermometer reads 140°, 10-15 minutes longer, occasionally brushing with glaze. Serve remaining glaze with sliced ham.