It can be done. There are a few members here (OrionGirl and Caz) who have very nice 10-gallon "nano-reefs." Several inches of sand, about 15 lbs of live rock, and 50-100 watts of PC lights will do the job nicely. It will be easier to keep witout fish, but it is possible.
I must add that those mentioned have a "bunch" of experience at the hobby, a ten gallon salt tank in my understanding is a very "touchy: system. Just some advice
I generally see that most of the "pros" suggest at least a 20 gallon for a clown fish. There may be some gobies that can take to a 10 gallon much more easily, but generally 10 and smaller is just for inverts.
ive got a 2 gallon reef, so easy, i havent had to change the filter yet its been 5 months, ibe got a juv. clown and bi color blenny, they are happy but i feel sorry for them anyways, they are goin in a 30 cube