Learn working of the kidneys (5)

I believe the answer is:

renal

'of the kidneys' is the definition.
(renal means relating to the kidneys)

'learn working' is the wordplay.
'working' indicates an anagram.
'learn' is an anagram of 'RENAL'.

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

I've seen this clue in The Times.

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