As far as I know there are not many good law colleges in Dehradun. The tag from being a great college always helps in the career.
I would advise you to evaluate yourself, or have someone evaluate you. If the result is that you may be able to get a decent NLU next year, do not hesitate in preparing for the CLAT next year. In the meanwhile, you may enroll in a college so that you do not feel you wasted your one year, if by some chace you are unable to make it next year.
Best of Luck.