Unpreventable ban or exile abroad (10)
I believe the answer is:
inexorable
'unpreventable' is the definition.
(thesaurus)
'ban or exile abroad' is the wordplay.
'abroad' is an anagram indicator (letters move around or go abroad).
'ban'+'or'+'exile'='banorexile'
'banorexile' is an anagram of 'INEXORABLE'.
(Other definitions for inexorable that I've seen before include "Relentless" , "Unrelenting" , "Inescapable" , "Harsh" , "Impossible to stop" .)