Lady in pub's imbibing singles ... (8)
I believe the answer is:
baroness
'lady' is the definition.
(I know that baroness is a type of lady)
'pub's imbibing singles' is the wordplay.
'pub's' becomes 'bar's' (both are drinking establishments).
'imbibing' is an insertion indicator.
'singles' becomes 'ones' ('one' can be a synonym of 'single').
'bars' enclosing 'ones' is 'BARONESS'.
'in' is the link.
(Other definitions for baroness that I've seen before include "Thatcher possibly" , "Woman life-peer" , "Aristocrat" , "Peer's title" , "Titled lady" .)