Welcome Turbostud653!
Clownfish do not need an anemone. Most anemones need strong light. I have had good luck with Rock Flower anemones in nanos under PC lighting but clowns do not host in them. I have had clowns host in many corals such as Hammer, Frogspawn, Toadstool & Lobophytum leathers, Green Star Polyps, Pom Pom Xenia and others. All of those do well in a nano.
Mike