Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
Stir brown sugar, pecans, butter, flour, cinnamon, cloves, and nutmeg together in a bowl to make crunch mixture.
Mix yellow cake mix, pumpkin, eggs, and water together in a separate bowl until batter is smooth. Pour half of the batter into the prepared baking dish; top with crunch mixture. Pour remaining batter over crunch.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 30 to 35 minutes.
Whisk confectioners' sugar and milk together in a small bowl, adding more milk if needed to reach a pourable consistency; drizzle over the cake.
