Cryptic Crossword by sain't

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Across
  1. 6. Back up fool that received part of fist. (6)
  2. 7. Enthusiasm is forever veiled within. (5)
  3. 10. Happiness by chance found in weirdly deserving sympathy, still not good. (11)
  4. 12. Fascinating invoice divided in expenditure. (11)
  5. 14. Unnamed authors spirit writhers without stop. (12)
  6. 16. Striking a deal at a tavern, huge success. (7)
  7. 19. Exclude man for bidding with others money. (6)
  8. 20. 24-7 lifestyles even teenagers copy. (9)
Down
  1. 1. Controversies announced, attitude indicates. (4,6)
  2. 2. Enthusiast eager for overtime. (6)
  3. 3. Gadget wildly zooming but is not on. (5)
  4. 4. Try small yet plenty. (6)
  5. 5. Comedy icon, master, king, hit person. (2,4)
  6. 8. Stamp of female leader had one stroke at birth. (7)
  7. 9. Chips scrambled carelessly. (6)
  8. 11. Theorized matter concerning silly lemma. (4)
  9. 13. Assuming form sample. (2,6)
  10. 15. One does not believe in heresy before sudden movement. (7)
  11. 17. Roman enemy reports two wildcards no longer south. (7)
  12. 18. Foreign by one's reversed logic. (4)