The word "oneseed" in the context of March Madness refers to a team that is ranked first in their respective region or division in the NCAA basketball tournament. In this case, the word "coveted" indicates that it is highly desired or sought after by teams because being a "oneseed" gives them certain advantages, such as playing weaker opponents in the early rounds or having potentially easier paths to the Final Four.
Note: The provided meaning of the answer is for the latest New York Times crossword puzzle clue: Coveted March Madness slot. Explanations are generated by AI and may be inaccurate.