Thus, at the West End, there's a boozer (3)
I believe the answer is:
sot
'a boozer' is the definition.
(both can mean an alcoholic)
'thus at the west end' is the wordplay.
'thus' becomes 'so' (synonyms).
'at' is a charade indicator (letters next to each other).
'end' suggests the final letters.
The last letter of 'west' is 't'.
'so'+'t'='SOT'
'there's' acts as a link.
(Other definitions for sot that I've seen before include "A chronic drinker" , "One's often intoxicated" , "Habitual drunkard" , "Boozer" , "Lush" .)