ONTO

In the process of finding out about (4)

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

• Quick crossword No 16,639 — 2023-09-03 23:00:24
  11A: About to discover (something secret) (4)
• Quick crossword No 15,887 — 2021-04-07 23:00:00
  7D: In the process of finding out about (4)