A few year ago I bought a Garrison flag at an auction. It has an old piece of paper(envelope) with it that reads, "Brother Clyde Killed in Action in Germany 1945." Any way I can narrow down who Brother Clyde actually might be?
That is going to nigh to impossible. Clyde was a fairly common name then and without a last name, the odds are going to be even higher with such a vague date and location to work with.
A search of the ABMC database yields over 50 results for US Army ETO burials with first name of Clyde and date of death in 1945. Of course, that assumes that his first name was Clyde. His family may have called him by his middle name. Also, a large number were repatriated for reburial in the USA after the War so, as Jeff said, it will be a virtually impossible task with so little specific info.