Say nothing about lawyers supporting mass prohibition (7)
I believe the answer is:
embargo
'prohibition' is the definition.
(I've seen this in another clue)
'say nothing about lawyers supporting mass' is the wordplay.
'say nothing' becomes 'ego' (I can't justify this - if you can you should believe this answer much more).
'about' indicates putting letters inside.
'lawyers' becomes 'bar' (the bar can refer to the legal profession).
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'mass' becomes 'm' (symbol used in Physics e.g. f=ma).
'bar' after 'm' is 'mbar'.
'ego' going around 'mbar' is 'EMBARGO'.
Can you help me to learn more?
(Other definitions for embargo that I've seen before include "Trading restriction" , "Legal stoppage of commerce" , "Prevent publication" , "Legal restraint" , "Admiralty order" .)