Asexual reproduction is a means through which a creature may reproduce itself without need of sexual contact with another. While a clone is a copy of a creature created without sexual contact, this process isn't exactly asexual reproduction. Asexual reproduction would refer to a creature doing this by itself, and naturally, as opposed to two cells being combined.
Tribbles are bisexual and are capable of reproducing at will. Born pregnant, and with sufficient food, a single tribble can breed in number exponentially, producing a litter of ten in twelve hours time. (TOS: "The Trouble with Tribbles")
Xindi-Insectoids reproduce asexually. (ENT: "Hatchery")