What does the cryptic crossword clue "Hormone turning in zucchini, not a lemon (9)" mean?

The definition is "Hormone". The wordplay uses a hidden word. hidden in reverse in zucchiNI NOT A LEMon. The answer is MELATONIN.

Hormone turning in zucchini, not a lemon (9)

Times Cryptic #28679 | 17 Down | 2023-08-11 flower