Learn arrangement of the kidneys (5)
I believe the answer is:
renal
'of the kidneys' is the definition.
(renal means relating to the kidneys)
'learn arrangement' is the wordplay.
'arrangement' is an anagram indicator.
'learn' is an anagram of 'RENAL'.
(Other definitions for renal that I've seen before include "Pertaining to the kidneys" , "associated with organ" , "Learn (anag) - of organs of the body" , "Referring to organ" , "Concerned with organ" .)