Sometimes, moisture can be 'squeezed' out of meringue by the heat of the oven browning process. It will also result in liquid in between the meringue and the filling.
Try two things: first, sprinkle a layer of cake crumbs on top of the filling before adding the meringue. and bake the meringue at a higher temp for a shorter period of time.
It may be a bit runny but its good to eat!
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan