SEMAPHORE

Old flag signalling system (9)

Solution has appeared in 2 crosswords (2 across and 0 down):

• Quick crossword No 15,842 — 2021-02-15 00:00:03
  5A: Make visual signals — a posher me (anag) (9)
• Quick crossword No 15,363 — 2019-08-02 23:00:36
  13A: Old flag signalling system (9)