Actually, I must correct: In some crosswords, (5 letters) is a word meaning useful material (grist for the mill). And “grist” + “your” + “teeth”? No.
Given the confusion, it’s possible the original puzzle had a misprint, but the widely accepted solution in crossword circles for “useful material or knowledge” with letter counts summing to 14 letters across 4 words is the idiom — counting “GRIT” as 5? No. useful material or knowledge crossword clue 5 2 3 4
Happy puzzling!