A defense was a legal procedure by which a defendant defended themselves against an allegation in a complaint or to charges in a charging instrument, such as an indictment. The defendant would present supporting evidence and arguments for why the allegations were not accurate and for why they should be set free.
Defense could, as well, be the defendant and their lawyer or lawyers.
In 2266, before his hearing aboard the USS Enterprise, Harcourt Fenton Mudd was informed by Captain James T. Kirk that Spock would supply him with any legal information he needed as he prepared for his defense. When Kirk asked Mudd for his defense, he responded, "Only heaven's own truth, which I've just given you." (TOS: "Mudd's Women")