VOLGA

Longest European river, flowing into the Caspian Sea (5)

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

• Quick crossword No 15,786 — 2020-12-10 00:00:32
  20D: Russian river flowing into the Caspian Sea (5)
• Quick crossword No 15,688 — 2020-08-17 23:00:21
  20A: Longest European river, flowing into the Caspian Sea (5)