WASHINGTON, July 14 (Reuters) - President Donald Trump secured approval of his first judicial nominee of his second term, as the U.S. Senate confirmed a former law clerk to three members of the U.S. Supreme Court's conservative majority to a seat on a federal appeals court. The Republican-led Senate voted 46-42 along party lines in favor of Whitney Hermandorfer, a lawyer serving under Tennessee's attorney general, to be appointed as a life-tenured judge on the Cincinnati-based 6th U.S. Circuit Court of Appeals.