Settler perhaps restraining road rage (8)
I believe the answer is:
emigrant
'settler' is the definition.
(thesaurus)
'perhaps restraining road rage' is the wordplay.
'perhaps' becomes 'eg' (for example).
'restraining' indicates putting letters inside.
'road' becomes 'mi'.
'rage' becomes 'rant'.
'eg' enclosing 'mi' is 'emig'.
'emig'+'rant'='EMIGRANT'
(Other definitions for emigrant that I've seen before include "One going abroad permanently" , "One leaving for another country" , "One who leaves to live in another country" , "One settling abroad" , "Write carelessly" .)