Obstruction or hostility (10)
I believe the answer is:
opposition
I believe this clue is a double definition.
'obstruction' is the first definition.
(I've seen this before)
'hostility' is the second definition.
(thesaurus)
(Other definitions for opposition that I've seen before include "organized political group" , "Enemy" , "antagonism" , "parliamentary group" , "those out of power" .)