Let's assume the answer is or similar. But without a specific crossword dictionary, let's look for idioms.
Check:
Meaning: Something useful to those who already understand. Perfect fit. useful material or knowledge crossword clue 5 2 3 4
Let me correct that: 5 2 3 4 would be something like: XXXXX (5) + XX (2) + XXX (3) + XXXX (4) . Let's assume the answer is or similar
"Useful material or knowledge" is a highly conceptual definition for a physical metaphor (a grain mill). Perfect fit
Maybe the clue is from a cryptic crossword where the numbers indicate the length of the answer words. The clue "useful material or knowledge" might be a definition for a phrase like "STUFF AND NONSENSE" but that's 5,3,8.
Let me search for the exact clue on a crossword database that shows answer patterns. There is a website "crossword-dictionary.com". Let me try..
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