Adverse criticism about southern vessel (5)
I believe the answer is:
flask
'vessel' is the definition.
(flask is a kind of vessel)
'adverse criticism about southern' is the wordplay.
'adverse criticism' becomes 'flak' (I've seen this before).
'about' means one lot of letters goes inside another.
'southern' becomes 's' (abbreviation).
'flak' enclosing 's' is 'FLASK'.
(Other definitions for flask that I've seen before include "Portable drink container" , "Glass container" , "Container for liquids" , "Small pocket bottle" .)