Don't criticise this object of worship (6,3)

I believe the answer is:

sacred cow

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(Other definitions for sacred cow that I've seen before include "Shibboleth" , "Hallowed bovine in India or revered institution" , "A hallowed institution like Indian bovine" , "one not to be criticised" , "counterpart of papal bull?" .)

I've seen this clue in the Sydney Morning Herald.

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