What does the cryptic crossword clue "Fateful day Cockney goes to ground? (4)" mean?

The definition is "Fateful day". The wordplay uses a deletion. IDES (deletion) = IDES; definition: "Fateful day" The answer is IDES.

Fateful day Cockney goes to ground? (4)

Times Cryptic #28735 | 10 Across | 2023-10-16 flower