Not amenable to discipline (6)
I believe the answer is:
unruly
'not amenable to discipline' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for unruly that I've seen before include "Difficult to control" , "Noisy and undisciplined" , "Disobedient and disruptive" , "Obstreperous" , "Not amenable to discipline" .)