Me upset on British boat to restrict trade (7)
I believe the answer is:
embargo
'restrict trade' is the definition.
(I've seen this before)
'me upset on british boat' is the wordplay.
'upset' says the letters should be written backwards.
'on' says to put letters next to each other.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'boat' becomes 'argo' (I've seen this before).
'me' reversed gives 'em'.
'em'+'b'+'argo'='EMBARGO'
'to' acts as a link.
(Other definitions for embargo that I've seen before include "Official ban or blockade on trade" , "Prohibit" , "Trade barrier or publication ban" , "Ban; prohibition" , "Commercial break" .)