Hard to control (6)
I believe the answer is:
unruly
'hard to control' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for unruly that I've seen before include "Not amenable to discipline" , "Boisterous, uncontrollable" , "Disobedient and disruptive" , "Not disciplined" , "Indisciplined" .)