Slur, slight (6)
I believe the answer is:
insult
I believe this is a double definition.
'slur' is the first definition.
(I've seen this in another clue)
'slight' is the second definition.
(to slight someone is to insult or disrespect them)
(Other definitions for insult that I've seen before include "Slander" , "Affront, offend" , "Cause offence to" , "An addition to injury?" , "Abusive remark" .)