Preheat the oven to 400 degrees F (200 degrees C.)

Arrange apple slices in unbaked pie shell. Mix 1/2 cup sugar and cinnamon; sprinkle over apples.

To make the crumble topping: Place 1/3 cup sugar and flour in a bowl. Cut in cold butter with 2 knives or pastry blender until the mixture resembles coarse crumbs; spoon mixture over apples.

Bake in preheated oven until apples are soft and top is lightly browned, about 40 minutes.