Clue: Blame shifted, after royal subject knocked over dearest possession (3-4)
Answer: EWE-LAMB
Explanation: Definition: dearest possession
Reverse of WE ("royal subject", as in the Royal We) + BLAME*. I see that the "dearest possession" sense has a biblical origin: in 2 Samuel 12 there is a story about "[a] poor man [who] had nothing, save one little ewe lamb, which he had bought and nourished up: and it grew up together with him, and with his children; it did eat of his own meat, and drank of his own cup, and lay in his bosom, and was unto him as a daughter." Spoiler alert: things don't turn out well for the ewe-lamb.