Improper treatment (6)
I believe the answer is:
misuse
'improper treatment' is the definition.
(wrong or improper use)
This is the entire clue.
(Other definitions for misuse that I've seen before include "Treat the wrong way or for the wrong purpose" , "Wrongful employment" , "Mistreat, misapply" , "Employ or apply wrongly" , "Poor treatment" .)