Harsh, tyrannical (10)
I believe the answer is:
oppressive
This clue is a double definition.
'harsh' is the first definition.
(thesaurus)
'tyrannical' is the second definition.
(I know that tyrannical can be written as oppressive)
(Other definitions for oppressive that I've seen before include "Harsh, authoritarian" , "Sultry" , "Difficult to bear" , "overpowering!" , "cruel" .)