ATOLL

Coral island surrounding a lagoon (5)

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

• Quick crossword No 15,720 — 2020-09-23 23:00:02
  9A: Ring-shaped coral reef (5)
• Quick crossword No 15,336 — 2019-07-02 23:00:22
  3D: Coral island surrounding a lagoon (5)