Ban traveller at last in international order (9)
I believe the answer is:
interdict
'ban' is the definition.
(thesaurus)
'traveller at last in international order' is the wordplay.
'at last' says to take the final letters.
'in' indicates putting letters inside.
'international' becomes 'int'.
'order' becomes 'edict' ('edict' can be a synonym of 'order'**).
The final letter of 'traveller' is 'r'.
'int'+'edict'='intedict'
'r' inserted inside 'intedict' is 'INTERDICT'.
(Other definitions for interdict that I've seen before include "Court order" , "An authoritative prohibition, maybe by church" , "Prohibit - tin credit (anag)" , "Prohibit, forbid" , "Ban" .)