Depends if it's important to the book. Usually it's not, but sometimes it is. But if you don't describe the clothes, check to see if there are enough cues to let the reader make something up. For example, a farmer might dress in all kinds of ways, but if you introduce a character and say he's a farmer, readers will assume certain clothing. If that's more or less accurate, you're good, unless something about clothing is important for this story. If readers can't guess at all, you may need to help them out a little.