Let me re-evaluate the word count.
Given the ambiguity, the most likely phrase that fits “useful material or knowledge” and letter pattern 5,2,3,4 is: useful material or knowledge crossword clue 5 2 3 4
Given 5,2,3,4: ? HARD (4 — no).
If you’ve encountered the clue with those specific letter counts, you are not looking for a single word. You are looking for a phrase —a four-word expression, with word lengths of five letters, two letters, three letters, and four letters respectively. Let me re-evaluate the word count