Clark's Regt was the successor of Clarkson's Battalion that was decimated at Locust Grove, Cherokee Nation in June 1862. This was the event that led to the mass defection of Drew's 1st Cherokee Mtd Rifles. David Haimerl literally "wrote the book" on Clarkson's Battalion. If you can get your hands on his book or contact David, he may be able to help.
Do you know when David E. Brown came to the Cherokee Nation?