Beers smug drunk sinks (9)
I believe the answer is:
'sinks' is the definition.
(submerging is a kind of sinking)
'beers smug drunk' is the wordplay.
'drunk' indicates anagramming the letters.
'beerssmug' with letters rearranged gives 'SUBMERGES'.
(Other definitions for submerges that I've seen before include "Dunks", "Goes under, sinks".)