Rebellious pair hated segregation (9)
I believe the answer is:
apartheid
'segregation' is the definition.
(apartheid is a kind of segregation)
'rebellious pair hated' is the wordplay.
'rebellious' indicates anagramming the letters.
'pair'+'hated'='pairhated'
'pairhated' is an anagram of 'APARTHEID'.
(Other definitions for apartheid that I've seen before include "System of segregation formerly practised in South Africa" , "Former South African system of racial separation" , "Network of bars no longer" , "Social policy of racial segregation" , "South Africa's former social policy - hit parade (anag)" .)