Lots of websites – for example, WorldAtlas.com – agree that Venus is the only planet that rotates clockwise. But many say that there are two: Venus and Uranus. I found several of the latter by googling "planets that rotate clockwise". (The same search also found plenty that say Venus is the only one, including WorldAtlas.)
No less an authority than NASA's Solar System site appears to come down on the side of two, stating that "Like Venus, Uranus rotates east to west." It adds, "Uranus is unique in that it rotates on its side"; and this may well be the reason for the confusion.
But hang on a minute. Is "rotat[ing] east to west" the same as "rotat[ing] clockwise"?
Well: whether it's rotating clockwise or anti–clockwise would depend on whether you're looking from above the north pole or the south pole.
Let's imagine we're in a spaceship hovering above the equator of a planet, with the north pole above and the south pole below (which is the normal way for planets to be depicted). If the planet is rotating "east to west", the rotation would appear to be from right to left.
If we now imagine moving our spaceship to a position above the north pole (while the planet, of course, keeps rotating in the same direction), I think the planet would appear to be rotating clockwise. In other words, rotating east to west is the same as rotating clockwise (if you're looking from above the north pole).
So: if Venus and Uranus both rotate from east to west (which NASA says they do), and Venus rotates (or spins) clockwise (which the question setter says it does), then so does Uranus.
The fact that Uranus "rotates on its side" doesn't change any of this. Uranus still has a north pole and a south pole: according to Wikipedia, "the north pole of a planet or satellite is the pole that points above the invariable plane of the Solar System". Uranus's axis is still at an angle to the invariable plane (the plane in which the planets orbit the Sun) – albeit a relatively small one; so one pole is above the plane, and one is below.
To say that a planet rotates east to west (as NASA does) is meaningless unless you've defined which is the north pole and which is the south; and if Uranus does rotate east to west, then from above its north pole it will appear to be rotating clockwise.
I know that when this question is asked in a quiz, the answer given is always Venus. But several websites effectively say that Uranus is an equally acceptable answer, and I reckon they have NASA on their side.
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