Stir first 6 ingredients in large bowl. Add pears and toss to coat. Whisk flour, sugar and cinnamon in medium bowl. Add butter and rub in with fingertips until mixture resembles coarse meal. Mix in nuts. Preheat oven to 375°F. Spoon pear filling into pie crust. Sprinkle topping evenly over filling. Bake pie 15 minutes. Reduce oven temperature to 350°F. Continue baking pie until pears are tender and filling is bubbling thickly, covering edges with foil if crust is browning too quickly, about 1 hour 5 minutes longer. Cool pie on rack at least 2 hours. Serve slightly warm or at room temperature.