Asks about Vilnius's top low-alcohol drink (5)
I believe the answer is:
kvass
'drink' is the definition.
(kvass is a kind of drink)
'asks about vilnius's top' is the wordplay.
'about' is an anagram indicator.
'top' suggests taking the first letters (in a down clue, the first letter is top).
The first letter of 'vilnius' is 'v'.
'asks' with its letters anagrammed with 'v' gives 'KVASS'.
'low-alcohol' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Another definition for kvass that I've seen is " Russian rye drink".)