Exclude from a group (9)
I believe the answer is:
ostracise
'exclude from a group' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ostracise that I've seen before include "Socrates and I are made to exclude from society" , "Exclude from a group or society" , "Banish from group" , "Cast out, send to Coventry" , "Shun, exclude" .)