Ostracize (4)
I believe the answer is:
snub
'ostracize' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for snub that I've seen before include "Reject or humiliate person" , "Insult; blunt (nose)" , "Pointedly rebuff" , "Give (someone) the cold shoulder" , "Blank" .)