You should be feeding all of the foods suggested by XSeaNX anyways, not just to try to get him eating.
vudu is right as well. Clowns are schooling fish, they like groups. What size is your tank BTW? These fish get large.
Don't be fooled by misinformed individuals who will tell you that they only reach a certain size in captivity. When provided with correct conditions, they will reach their adult size of 12" easily.
I have 5 clowns in a 180g community tank. I feed them frozen bloodworms, shrimp pellets, color enhancing pellets, freeze dried tubifex worms, live black worms (very rarely), live brineshrimp, cucumber, leaves of lettuce, and mango slices (occasionally).
HTH