George-no evidence of a your man, however, he would have been only 13 in 1861, he would not have been liable for military service until 1864 at the earliest. Except for a pair in the Federal 8th TN. Inf, all the other McClard(e)'s in Tennessee service served in Company "G", 30th Tennessee, recruited in Macon County.
In spite of myths to the contrary, 13-16 year olds were extremely rare in CW period units. Only late in the war did the Confederacy lower the conscription age to 17. By the time Caleb was old enough to fight, Tennessee had been under federal control for 3 years. Not a lot of oppurtunity to join up would have been avialable to him.