Hostile reaction (8)
I believe the answer is:
backlash
'hostile reaction' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for backlash that I've seen before include "Sudden violent reaction to an action or situation" , "Strong negative reaction to a development" , "Provoked adverse reaction" , "Violent reaction to an event - using whip?" , "Hostile reaction" .)