How can you patent a novel piece of clothing?
In simple terms, a utility patent can protect the way something works or some inherent technical feature of the clothing. A design patent protects the aesthetic features of the clothing.
As an example of “the way something works”, I drafted a specification and patented on behalf of my client a garment designed for people who were disabled and could not stand up. The essence of the invention was a technical one, namely a way of designing the garment so that these could be fitted onto the person without the need to move them.
Fashion items are often more ornamental in nature and are more appropriately covered by design patents (also called registered designs in many non-US jurisdictions).