Briefly board ship prior to travel ban (7)
I believe the answer is:
embargo
'ban' is the definition.
(thesaurus)
'briefly board ship prior to travel' is the wordplay.
'briefly' means to remove the last letter.
'board ship' becomes 'embark' (I've seen this before).
'prior to' means one lot of letters go next to another.
'travel' becomes 'go' ('go' can be a synonym of 'travel').
'embark' with its last letter taken away is 'embar'.
'embar'+'go'='EMBARGO'
(Other definitions for embargo that I've seen before include "Trade barrier or publication ban" , "Official prohibition as on trade" , "Ban, veto" , "Official ban on trade or commerce" , "Eg, Rambo? (anag)" .)