Barker to misbehave, brought into line (7)
I believe the answer is:
terrier
'barker' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for terrier that I've seen before include "Reserve soldier" , "Small, short-bodied dog" , "he's not a boxer" , "Dog - old land register" , "part-timer in Services" .)