"THEDA" is a term that refers to "The District Attorney." In the context of the given clue, the term "THEDA" is a familiar, shortened form for "The District Attorney" and represents the opposing lawyer that a public defender might face in court.
Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Whom a public defender might go up against, familiarly. Explanations are generated by AI and may be inaccurate.