Disapproving sound is about race (5)
I believe the answer is:
tutsi
'race' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'disapproving sound is about' is the wordplay.
'disapproving sound' becomes 'tut' (sound made to express disapproval).
'about' shows that the letters should be reversed in order.
'is' in reverse letter order is 'si'.
'tut'+'si'='TUTSI'
Can you help me to learn more?
(Other definitions for tutsi that I've seen before include "Rwandan Bantu" , "tribesman" , "member of a Bantu tribe" , "Ethnic group of Rwanda and Burundi" , "Bantu speaking people of Rwanda and Burundi" .)