Is there a planet named 'Clara' outside the orbit of Pluto?

No. There is no known object similar to, or larger in size to Pluto that is any closer than about 2-3 times the present orbital distance of Pluto. Its infrared emissions and gravitational influences would have been detected by now...and they haven't despite a LOT of searching.

You might be thinking of the satellite to Pluto called Charon. There are also two large bodies called Quaoar and Varuna that are between 500 and 900 miles across....but no Clara!

Here's a current map of the known objects beyond the orbit of Neptune. The circles are the orbits for Jupiter, Saturn Uranus and Neptune. Can you find Pluto? It's getting pretty crowded out there!!