Primary schools are indebted to a South African urban area (6)
I believe the answer is:
soweto
'a south african urban area' is the definition.
The definition suggests a singular noun which matches the answer.
'primary schools are indebted to' is the wordplay.
'primary' suggests taking the first letters.
'are indebted' becomes 'owe' (I can't explain this - if you can you should believe this answer much more).
The first letter of 'schools' is 's'.
's'+'owe'+'to'='SOWETO'
Can you help me to learn more?
(Other definitions for soweto that I've seen before include "Group of townships in South Africa" , "South African township area" , "Township in Johannesburg" , "place in Africa" , "Scene of 1976 riots southwest of Johannesburg" .)