clen is classified as a steroid, so you wont be "clean" anymore. Other than that clenbuterol is a fat burner, so if you are looking to shed some pounds then go for it.
I would go with T3 and Clen.... T3 for 35-42 days in a pyramid, and clen, 2 weeks on 2 weeks off.... Slowly work up on the doses, you should burn a good amount of fat with this and get the ripped look.
I doubt that you are natural. And you better get ripped really fast becasue at 12% you got a good ways to go to compete. Im calling bullshit on this one.