Bar’s words from member with drinks on tab (8)
I believe the answer is:
legalese
'bar's words' is the definition.
(the bar can mean the legal profession)
'member with drinks on tab' is the wordplay.
'member' becomes 'leg' (member can mean a limb).
'with' says to put letters next to each other.
'drinks' becomes 'ales' (ale is a kind of drink).
'on' means one lot of letters go next to another.
'tab' becomes 'e' (ecstasy or E is a type of tab or tablet).
'leg'+'ales'+'e'='LEGALESE'
'from' is the link.
(Other definitions for legalese that I've seen before include "barman's peculiar words" , "it's hard for most to understand" , "Special terms" , "contract wording?" , "Bar talk" .)