Alternatively, some puzzles give the answer as but that doesn’t match (5,2,3,4) because “ONE’S” is 4 letters, not 2.

Thus, the clue is a trick:

Check the Prepositions: Small words like "to," "the," "of," or "in" often act as the skeleton of the answer.

(known from crossword databases):

The final page read: “This is the true Store of Wisdom – useful material (clean water, medicinal roots, fire starters) bound with knowledge (when to harvest, how to preserve). If you solved the crossword clue, you earned the right to find this. Use it well.”