Side by side in bar seat, both drunk (7)
I believe the answer is:
abreast
'side by side' is the definition.
('abreast' can be a synonym of 'side by side')
'bar seat both drunk' is the wordplay.
'both drunk' indicates an anagram (I've seen this in other clues).
'bar'+'seat'='barseat'
'barseat' with letters rearranged gives 'ABREAST'.
'in' is the link.
(Other definitions for abreast that I've seen before include "Familiar" , "shoulder to shoulder" , "Well-informed" , "Level or keeping pace with" , "On a level together" .)