1. Preheat oven to 375°F. In a large bowl mix 1 cup white sugar with 6 Tbsp flour, orange zest, cinnamon, nutmeg, and salt. Use a slotted spoon to transfer currants from brandy (reserve the brandy) to the sugar mixture. Add cranberries and apples and mix well. Pour filling into unbaked pie pastry and drizzle with the reserved brandy.
2. In another bowl mix 1 cup flour with 2/3 cup of brown sugar. Add the butter and cut in with a pastry blender or rub with your fingers until the mixture forms small lumps. Sprinkle topping over the filling. Set pie in a foil-lined 10x15 inch baking pan (to catch the juices).
3. Bake on bottom rack until juices bubble, 55 to 65 minutes. If pie browns too quickly, cover loosely with foil.
4. Set pie on rack, uncovered, to cool for 2 to 3 hours.