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What gives tonic water its taste (7)

Solution has appeared in 3 crosswords (1 across and 2 down):

• Quick crossword No 16,390 — 2022-11-17 00:00:33
  16D: Bitter alkaloid used in tonic water (7)
• Quick crossword No 15,660 — 2020-07-15 23:00:16
  21A: Cinchona bark extract used to treat malaria (7)
• Quick crossword No 15,532 — 2020-02-18 00:00:11
  6D: What gives tonic water its taste (7)