Blackballed (10)
'blackballed' is the definition.
('ostracize' can be a synonym of 'blackball')
This is all the clue.
'blackballed' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for unwelcome that I've seen before include "Not gladly received" , "No received with pleasure - by host?" , "Causing displeasure" , "not willingly admitted" , "Bad (news); not acceptable" .)