In a medium bowl, combine flour, oats, brown sugar, cinnamon and nutmeg. Stir in butter. Place half of the crumble in the bottom of a greased 8x8 square baking pan.

In a small saucepan, whisk sugar with constarch, then whisk in water. Bring to a boil, then reduce heat to medium-low and continue to cook, whisking constantly, for 5 minutes, or until sauce thickens and becomes clear.

In a large bowl, toss together fruit. Spread over the crumble base. Pour sauce over fruit and sprinkle with remaining crumble.

Bake in 350°F oven for 50 minutes or until apples are tender.

Serve warm with vanilla ice cream.