Stop swallowing most of beer, it's common (9)
I believe the answer is:
prevalent
'common' is the definition.
(thesaurus)
'stop swallowing most of beer' is the wordplay.
'stop' becomes 'prevent' (I've seen this before**).
'swallowing' indicates putting letters inside.
'most of' means to remove the last letter.
'beer' becomes 'ale' (I've seen this before).
'ale' with its final letter removed is 'al'.
'prevent' enclosing 'al' is 'PREVALENT'.
'it's' acts as a link.
(Other definitions for prevalent that I've seen before include "Commonplace" , "Widespread - current" , "general" , "Common" , "powerful" .)