What does the cryptic crossword clue "Repudiate participants in Greek overreaction after upheaval (6)" mean?

The wordplay uses a hidden word. Backwards hidden in [gre]EK OVER[eaction]. The answer is REVOKE.

Repudiate participants in Greek overreaction after upheaval (6)

Times Cryptic #28879 | 20 Down | 2024-04-01 flower