Grub freed from unpopular VAT (5)
I believe the answer is:
larva
'grub' is the definition.
(I know that grub can be written as larva)
'from unpopular vat' is the wordplay.
'from' indicates a hidden word.
'LARVA' is hidden within 'unpopular vat'.
'freed' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for larva that I've seen before include "Immature form of an insect before metamorphosis" , "Early stage of creature" , "Immature form of caterpillar" , "E.g. caterpillar form" , "Immature life form" .)