Ban, for example, Oscar keeping mass drinking haunt (7)
I believe the answer is:
embargo
'ban' is the definition.
(I know that embargo is a more specific form of the action ban)
'example oscar keeping mass drinking haunt' is the wordplay.
'example' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'keeping' is an insertion indicator.
'mass' becomes 'm' (symbol used in Physics e.g. f=ma).
'drinking haunt' becomes 'bar' (a bar is a drinking establishment).
'eg'+'o'='ego'
'm'+'bar'='mbar'
'ego' placed around 'mbar' is 'EMBARGO'.
'for' is the link.
(Other definitions for embargo that I've seen before include "Official prohibition as on trade" , "Ban on commerce - mob rage (anag)" , "Legal stoppage of commerce" , "Trading restriction" , "Government trade ban" .)