51.

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Across
  1. 1. Raises the roof
  2. 5. Raise the roof about student coming bottom (5)
  3. 7. Figure of speech like "raise the roof" or "hit the ceiling"
  4. 9. Raise the roof
  5. 11. Group that raises the roof?
  6. 12. OF A TIME Great fun to be had with wheatmeal, if nothing's substituted (5,2,1,4)
  7. 14. Explosion is great fun
  8. 16. It may raise the roof
Down
  1. 2. Raise the roof
  2. 3. What Charon ferries across the river Styx to Hades
  3. 4. Shift party may raise the roof - or is that raze? (5,7)
  4. 6. Raise the roof with lifting tool
  5. 8. All this is admitting what outstanding bills are
  6. 10. YES Fan's cry after a great play
  7. 11. Act it in play? It's exposed, if you raise the roof(5)
  8. 12. A jetty for ferries to dock at (5)
  9. 13. Raise the roof
  10. 15. WE Bon Jovi "___ gonna raise the roof?"
  11. 17. ICE What "neat" means in a drink order