definitely not in a 75. Clown tangs are aggressive and very difficult to care for. If one is able to survive in that small of a tank (which is highly unlikely as is) they will harass anything that occupies their space.
one of my friends had a clown tang in his 180 and it was ok when small (~1.5"-2") but once it started to get bigger it pounded on everything and he had to get rid of it...I can tell you i would not put one in my 210!