Young troublemaker (8)
I believe the answer is:
hooligan
'young troublemaker' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for hooligan that I've seen before include "Destructive or badly-behaved youth" , "Thug, ruffian" , "Yobbo" , "Rowdy yob" , "Wild ruffian" .)