The crossword question “One of three in many baseball fields is ACRE” refers to the size of a baseball field, which is typically measured in acres. A standard baseball field is made up of three main parts – the infield, the outfield, and foul territory. The infield is the innermost part of the field and typically measures about one acre in size. The outfield surrounds the infield and can vary in size, but is typically much larger than the infield. Finally, foul territory refers to the areas outside of the playing field, where balls hit out of bounds are considered foul balls. Therefore, the answer to this crossword question is ACRE, as it refers to the size of one of the three main parts of a baseball field.