Ban British in game, or otherwise (7)
I believe the answer is:
embargo
'ban' is the definition.
(I know this)
'british in game or otherwise' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'in' means one lot of letters goes inside another.
'otherwise' indicates an anagram.
'game'+'or'='gameor'
'gameor' with letters rearranged gives 'emargo'.
'b' going into 'emargo' is 'EMBARGO'.
(Other definitions for embargo that I've seen before include "Official order forbidding something" , "Stop" , "Eg, Rambo? (anag)" , "Commercial ban" , "Government order imposing a trade barrier" .)