Pretty much as Flare said. You COULD get creative and have "defenders" of a sort. For example, you can train wolves to fight for you, or a big furry lizard-ox called "Lox" later on. You can also dig pits and trap larger enemies in there, and have them hold the aggro of some other approaching enemies. (Like having Trolls or Golems guard against Skeletons, blobs, and other monsters that will occasionally try to raid your base).

I get really wrapped up in trying to devise new defenses.