Race in the sprawling metropolis (9)
I believe the answer is:
ethnicity
'race' is the definition.
(I've seen this before)
'in the sprawling metropolis' is the wordplay.
'sprawling' indicates an anagram.
'metropolis' becomes 'city' (a metropolis is a large city).
'in'+'the'='inthe'
'inthe' with letters rearranged gives 'ethni'.
'ethni'+'city'='ETHNICITY'
(Other definitions for ethnicity that I've seen before include "Racial origin" , "Cultural background" , "race" , "Cultural identity" .)