ESSENTIAL

Key (9)

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

• Quick crossword No 16,370 — 2022-10-24 23:00:19
  12D: Sine qua non (9)
• Quick crossword No 15,659 — 2020-07-14 23:00:28
  21A: Key (9)