Afraid to bring up a bully who's beyond reproach (6,3)
I believe the answer is:
sacred cow
'beyond reproach' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'afraid to bring up a bully' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
'bully' could be 'cow' (cow can mean to bully or oppress) and 'cow' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'who's' acts as a link.
Can you help me to learn more?
(Other definitions for sacred cow that I've seen before include "Person or institution held to be above criticism" , "Object of irrational veneration" , "One unreasonably held to be above criticism" , "Facing this, carp not" , "Object beyond criticism" .)