Some brothels in kingdom's capital city (8)
I believe the answer is:
helsinki
'capital city' is the definition.
(capital of Finland)
'some brothels in kingdom's' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'HELSINKI' is hidden within 'brothels in kingdoms'.
(Other definitions for helsinki that I've seen before include "European capital, venue for the 1952 Olympics" , "North European capital" , "Foreign city" , "foreign capital" , "Finnish capital" .)