Green tea brewed for a youngster (8)
I believe the answer is:
teenager
'for a youngster' is the definition.
(I've seen this before)
'green tea brewed' is the wordplay.
'brewed' is an anagram indicator.
'green'+'tea'='greentea'
'greentea' anagrammed gives 'TEENAGER'.
(Other definitions for teenager that I've seen before include "14, perhaps" , "one that's not yet made a score?" , "Youngster" , "hormonal problem?" , "troublesome youth" .)