Penal; retaliatory (8)
I believe the answer is:
punitive
I believe this clue is a double definition.
'penal' is the first definition.
(similar in meaning)
'retaliatory' is the second definition.
(thesaurus)
(Other definitions for punitive that I've seen before include "Inflicting penalties" , "As deterrent, retribution" , "Penal; crippling" , "Severe and retaliatory" , "intended to teach a lesson" .)