Ban eastern doctor associated with Jason’s ship (7)
I believe the answer is:
embargo
'ban' is the definition.
(I've seen this before)
'eastern doctor associated with jason's ship' is the wordplay.
'eastern' becomes 'e'.
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'associated with' says to put letters next to each other.
'jason's ship' becomes 'argo' (ship in Greek myth).
'e'+'mb'+'argo'='EMBARGO'
(Other definitions for embargo that I've seen before include "Eg, Rambo? (anag)" , "Block" , "Commercial break" , "Stop" , "Ban; prohibition" .)