South American city rich in opportunity, initially (3)
I believe the answer is:
rio
'south american city' is the definition.
(I've seen this before)
'rich in opportunity initially' is the wordplay.
'initially' indicates taking the first letters.
The first letters of 'rich in opportunity' is 'RIO'.
(Other definitions for rio that I've seen before include "Port, -- de Janeiro" , "Brazilian city and port" , "old capital" , "Erstwhile home of Biggs" , "The ... Grande borders Texas and Mexico" .)