Untax beer? That could make you full of vitality! (9)
I believe the answer is:
exuberant
'full of vitality' is the definition.
(exuberance is vitality or liveliness)
'untax beer? that could make you' is the wordplay.
'that could make you' is an anagram indicator.
'untax'+'beer'='untaxbeer'
'untaxbeer' anagrammed gives 'EXUBERANT'.
(Other definitions for exuberant that I've seen before include "Exeunt bar, being in high spirits" , "Full of energy, high spirits" , "Lively, cheerful" , "Elated" , "Abounding in vitality" .)