Clover is a human child who wears a leather jacket, blue (presumed jeans) pants, a yellow bandana with blue polka-dots, brown shoes, and a brown cowboy hat. They seem to have short-sized brown hair with a ponytail, pale skin, and a neutral expression. According to official art for the game, Clover has yellow irises.
Little is known about Clover's personality as of yet. However, as their SOUL trait is Justice and they have a cowboy motif, it is likely that Clover has an affinity for history and the wild west, alongside seeking to preserve the law.
Because the Fallen Child will not play a role in UNDERTALE YELLOW, it is safe to assume that Clover will develop more hostile and violent traits much like Frisk, during a Genocide route.
Similarly, not much is known about Clover's abilities. However, the developers have stated that Justice will play a role in the game. As Clover main trait isn't Determination, Flowey saves the game for them.Their starting equipment, the Gun and the Cowboy Hat, is the second most powerful equipment in Undertale, but provide no changes to AT or DF. Instead, the Gun and Cowboy hat can be equipped with different kinds of ammunition or accessories respectively. In Undertale, getting the Yellow flag in the "Ball" game will prompt text that says "Your sure-fire accuracy put an end to the mayhem of 'Ball.'" This suggests that Clover has adequate experience with gunfire or ranged weapons, which is likely the reason for the fight mechanics having a target.