Dotty conveners set out to ostracise (4,2,8)
I believe the answer is:
send to coventry
'ostracise' is the definition.
(thesaurus)
'dotty conveners set out' is the wordplay.
'set out' is an anagram indicator.
'dotty'+'conveners'='dottyconveners'
'dottyconveners' with letters rearranged gives 'SEND TO COVENTRY'.
'to' acts as a link.
(Other definitions for send to coventry that I've seen before include "blank" , "exclude" , "Ostracise" , "Ignore" .)