Speak rudely or offensively to (6)
I believe the answer is:
insult
'speak rudely or offensively to' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for insult that I've seen before include "Slander" , "Speak or act in way designed to hurt" , "Cause offence to" , "Remark intended to hurt or humiliate" , "A deliberately offensive remark" .)