City spa a Dane transformed (8)
I believe the answer is:
pasadena
'city' is the definition.
(Pasadena is a city in California)
'spa a dane transformed' is the wordplay.
'transformed' indicates an anagram.
'spa'+'a'+'dane'='spaadane'
'spaadane' anagrammed gives 'PASADENA'.
(Other definitions for pasadena that I've seen before include "US city" , "California city of the Rose Bowl stadium" , "City in Los Angeles County" , "Californian city" , "place in California" .)