Class distinction is rejected, we hear (5)
I believe the answer is:
caste
'class distinction' is the definition.
(I've seen this in another clue)
'rejected we hear' is the wordplay.
'rejected' becomes 'cast' (to cast off or cast away is to reject).
'we hear' indicates a 'sounds like' (homophone) clue.
'cast' sounds like 'CASTE'.
'is' is the link.
(Other definitions for caste that I've seen before include "Religious or social class" , "Social group in India" , "Large, long-necked, wading bird" , "A sect (anag)" , "Social status" .)