Attack outspoken drunk? Not OK (3,4)
I believe the answer is:
set upon
'attack' is the definition.
(I know that set upon has the is a more specific form of the action attack)
I don't understand how the rest of the clue works.
(Other definitions for set upon that I've seen before include "Determined to do (something)" , "Attack" , "Attacked" , "Mug" .)