WELCOME to the site.
No, you do not need to put a clown with an anemone in a 2g tank. Try to set up AT LEAST a 55g, preferably paired with a sump for additional water volume. It will make your water parameters more stable, it will give the anemone enough room to grow and remain comfortable. I wouldn't put an H.Mag. in anything less than a 75g though to be honest.
If you can't afford a larger tank at the moment, don't get an anemone and clown. Stay with something small like a neon goby, yellow or green clown goby, green stripe goby or the like... Make sure you can meet the needs of your livestock choice first before making a decision on how big your tank needs to be.
See yah around!