You could just drag it to the trash, but then as you use LR, it will have to rebuild any preview that you need, which will be annoyingly slow, probably. None of your adjustments are contained in the preview folder. There's no way to selectively clean it out. I suppose you could delete the folder and then tell LR to rebuild it without 1:1 previews, but that could take a really long time and might not save you that much space. How many images do you have?
Are you that short on space? As people keep pointing out, disk is cheap.