Young person brewing green tea (8)
I believe the answer is:
teenager
'young person' is the definition.
(thesaurus)
'brewing green tea' is the wordplay.
'brewing' indicates an anagram.
'green'+'tea'='greentea'
'greentea' is an anagram of 'TEENAGER'.
(Other definitions for teenager that I've seen before include "14, perhaps" , "Youngster" , "troublesome youth" , "one no longer twelve?" , "one that's not yet made a score?" .)