Heat oven to 400°F. Place pie crust in 9-inch glass pie plate as directed on box for One-Crust Filled Pie.
In large bowl, lightly toss pears and remaining pie ingredients. If pears are very juicy, add additional 1 tablespoon flour. Spoon into crust-lined plate.
In medium bowl, mix 1/2 cup flour, the brown sugar, cinnamon, ginger and nutmeg. Cut in butter, using pastry blender or fork, until mixture is crumbly. Stir in walnuts. Spoon over pear mixture.
Cover crust edge with strips of foil to prevent excessive browning. Bake 35 to 45 minutes or until topping is golden brown. Cool at least 30 minutes before serving. Serve warm or cool.