Doctor is rude to stranger (8)
I believe the answer is:
outsider
'stranger' is the definition.
(outsider is a kind of stranger)
'doctor is rude to' is the wordplay.
'doctor' indicates an anagram.
'is'+'rude'+'to'='isrudeto'
'isrudeto' is an anagram of 'OUTSIDER'.
(Other definitions for outsider that I've seen before include "Not one of the favourites" , "Contestant who hasn't much of a chance" , "Not a member of the group" , "Improbable winner" , "Competitor rated as unlikely to succeed" .)