To start, understand that clownfish don't "need" anemone's. Also, there is no guarantee that the clown will even take to the anemone.
That being said, here is what they need in a nut shell.
1 - Excellent water quality
2 - Good circulation
3 - Strong lighting, preferably metal halide.
4 - Meaty foods such as squid, silversides, etc. fed several times a week.
5 - LR with crevices to attach to and hide under.