A sect reserved for a social class (5)
I believe the answer is:
caste
'social class' is the definition.
(caste is a kind of social class)
'a sect reserved' is the wordplay.
'a sect' anagrams to 'CASTE'.
However, I am unsure how this is indicated.
'for a' is the link.
Can you help me to learn more?
(Other definitions for caste that I've seen before include "Social group in India" , "Social position" , "Level in society" , "Social class in Hinduism" , "Social system" .)