What this will be is a blocked drain hole inside the freezer. So as that is blocked then the defrost water cannot drain out so it over flows and leaks out to under the bottom basket and then out the door like its doing.
What you need to do is either empty the freezer and from there you need to remove the plastic back panel inside the freezer.
Theres 2 panels so you need to remove both and behind there you will see the evaporator.
Under this is the drain gutter. It will be cover in ice so you need to melt all the ice in there.
Then in the middle you will see the drain hole. Pore boiling water in there and melt the ice. Poke something in there to clear it as well.
Once clear pore water in there and just check it can drain out.
Then refit the covers and thats it job done.
Or if you dont want to go removing panels then you need to empty the freezer and and turn it off for 24 hours and leave the freezer door open and this will defrost the ice in there itself.
Try that and you will find this will cure it. This is a very common fault on frost free appliances as i see it alot. If you need anymore info just get back to me.