DARKHORSE

Competitor about whose abilities little is known (4,5)

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

• Quick crossword No 16,131 — 2022-01-19 00:00:05
  7D: Little known runner? (4,5)
• Quick crossword No 15,282 — 2019-04-30 23:00:32
  12A: Competitor about whose abilities little is known (4,5)