Give the cold shoulder (6)
(Other definitions for shun that I've seen before include "Avoid, keep away from" , "Parade-ground language" , "Steer clear of" , "military command" , "Avoid contact" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">give the cold shoulder</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for snub that I've seen before include "Treat with disdain" , "Rude put-down; blunt (nose)" , "Reject greeting, seek to humiliate" , "unusually short" , "put down" .)
(Other definitions for rebuff that I've seen before include "Snub or contemptuous refusal" , "Ungraciously reject" , "Check" , "Reject bluntly" , "Ungracious rejection of a friendly approach" .)