What does the cryptic crossword clue "Grub freed from unpopular VAT (5)" mean?

The definition is "Grub". The wordplay uses a hidden word. Hidden in "grub freed from unpopuLAR VAt" The answer is LARVA.

Grub freed from unpopular VAT (5)

Guardian Cryptic #29100 | 20 Across | 2023-06-19 flower