A legal right to be a newcomer (5)
I believe the answer is:
alien
'newcomer' is the definition.
(thesaurus)
'a legal right to be a' is the wordplay.
'a legal right' becomes 'lien' (type of property right).
'to' says to put letters next to each other (I've seen this in other clues).
'lien' after 'a' is 'ALIEN'.
(Other definitions for alien that I've seen before include "24a [ESTRANGE]" , "One is from outer space, perhaps" , "Offensive" , "coming from overseas" , "Foreign (from outer space?)" .)