Gambling centre where pound note’s gone west (4)
I believe the answer is:
reno
'gambling centre' is the definition.
(I've seen this before)
'pound note's gone west' is the wordplay.
'pound note' becomes 'oner' (oner can mean a one pound note).
'gone west' says the letters should be written in reverse (letters written right to left or 'east to west').
'oner' back-to-front is 'RENO'.
'where' is the link.
(Other definitions for reno that I've seen before include "American city" , "Nevada city of Nero" , "Divorce capital of Nevada" , "Nevada marriage and divorce centre" , "gambling centre" .)