You don't. it will always be here as a memorial of how your failed clan. :P Or (As MrCookie would put it, so I can save him time from posting here again....) a memorial to how stupid you were for making a clan as equally stupid (that's the clean version for the little ones -_-)
But, you could always lock it by scrolling all the way down and hit the button that says lock/unlock topic. Best of luck for your future in blockland........
Mage's random Proverb of the Day:
"a journey of a thousand miles, starts with one step"
-Lao-tzu