Hateful criticism (7)
I believe the answer is:
vitriol
'hateful criticism' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for vitriol that I've seen before include "hostile criticism" , "Scathing criticism - sulphuric acid" , "Bitter words" , "Venomous language and an acid" , "Sulphuric acid or savage comment" .)