City currency invested in crooked casinos (3,9)
I believe the answer is:
san francisco
'city' is the definition.
(San Francisco is an example)
'currency invested in crooked casinos' is the wordplay.
'currency' becomes 'franc' (old French currency).
'invested in' means one lot of letters goes inside another.
'crooked' indicates an anagram.
'casinos' is an anagram of 'sanisco'.
'franc' placed within 'sanisco' is 'SAN FRANCISCO'.
(Other definitions for san francisco that I've seen before include "Californian city" , "US west coast port" , "hilly city" , "US city renowned for its cable cars" , "City of the Golden Gate Bridge" .)