What does the cryptic crossword clue "Insect almost turned on dog (8)" mean?

The wordplay uses a charade (building blocks). HORN (synonym="HORN") + TAIL (synonym="follow=”dog”") = HORNTAIL The answer is HORNTAIL.

Insect almost turned on dog (8)

Guardian Cryptic #29473 | 22 Across | 2024-08-28 flower