Hmm.......
Kill any bears you may find in the cave and build a small houselike entrance gate outside the cave.
I don't even know of that game...
By building a houselike gate outside the cave I mean make a house that covers up the cave with a hole or door to enter it. Also, if you will and can, build a trench around the workshop-house you made and build a bridge. Reccomended method: dig near the beach and make a river of water that leads around the house, build a bridge, then release the water.