Harshness of manner (8)
I believe the answer is:
asperity
'harshness of manner' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for asperity that I've seen before include "Irritability" , "Harshness or severity of manner" , "Harshness, bitter coldness" , "Roughness of temper" , "Roughness, bitterness" .)