Butcher nearly missing back of an organ (5)

I believe the answer is:

renal

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'of an organ' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for renal that I've seen before include "around the kidney" , "Referring to organ" , "Pertaining to the kidneys" , "Vital organ's" , "using the reins" .)

I've seen this clue in The Independent.

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