Confederate Veteran magazine, vol. XXIII (1915), p. 445, includes a brief story about Mrs. Amy Clark, who is said to have buried her husband "with her own hands" at Shiloh. He is not named here.
I find no evidence from the census or military records of either Amy or Walter Clark/Clarke, unless we are talking about Capt. Walter G. Clarke, Co. B, 4th Virginia Cavalry. I believe this officer survived the war and served in the eastern theater, so he must be someone else.
Where did you find this story?