Ban doctor boarding English ship in the past (7)
I believe the answer is:
embargo
'ban' is the definition.
(I know that embargo is a more specific form of the action ban)
'doctor boarding english ship in the past' is the wordplay.
'doctor' becomes 'MB' (Bachelor of Medicine, Medicinae Baccalaureus).
'boarding' indicates putting letters inside.
'english' becomes 'E' (abbreviation as in OED).
'ship in the past' becomes 'argo' (I am not sure about this - if you are sure you should believe this answer much more).
'e'+'argo'='eargo'
'mb' put into 'eargo' is 'EMBARGO'.
Can you help me to learn more?
(Other definitions for embargo that I've seen before include "Trading restriction" , "Admiralty order" , "Official ban on trade or commerce" , "Eg, Rambo? (anag)" , "restrict trade" .)