Apathetic teen intrudes furiously (12)
I believe the answer is:
uninterested
'apathetic' is the definition.
(similar in meaning)
'teen intrudes furiously' is the wordplay.
'furiously' indicates an anagram.
'teen'+'intrudes'='teenintrudes'
'teenintrudes' with letters rearranged gives 'UNINTERESTED'.
(Other definitions for uninterested that I've seen before include "indifferent" , "Apathetic" , "Bored" , "Not concerned" .)