Youngster throwing out green tea (8)
I believe the answer is:
teenager
'youngster' is the definition.
(thesaurus)
'throwing out green tea' is the wordplay.
'throwing out' indicates an anagram.
'green'+'tea'='greentea'
'greentea' with letters rearranged gives 'TEENAGER'.
(Other definitions for teenager that I've seen before include "troublesome youth" , "Young person" , "hormonal problem?" , "Adolescent" , "one with an unpredictable nature" .)