To clothe someone is to give them something to wear, or to dress them in clothing. If you clothe your dog in cute outfits, you may traumatize him for life.
You can clothe yourself, or someone else — for example, you might clothe yourself in black for a relative's funeral or clothe yourself in sequins and feathers for the school dance. You can also figuratively clothe someone or something, lending them a sense of power or respectability. Clothe shares a root with clothing and cloth, the Old English claþ, "cloth or sail," and also "woven material to wrap around oneself."