Gambling Mecca in Grenoble (4)
I believe the answer is:
reno
'gambling mecca' is the definition.
(I've seen this in another clue)
'in grenoble' is the wordplay.
'in' indicates a hidden word.
'RENO' is hidden in the letters of 'grenoble'.
(Other definitions for reno that I've seen before include "American city" , "City in Nevada known for gambling and easy marriage/divorce" , "City in Nevada known for casinos and easy divorces" , "City in Nevada known for casinos and easy divorce" , "gambling centre" .)