Learn layout of an organ (5)
I believe the answer is:
renal
'of an organ' is the definition.
(I've seen this before)
'learn layout' is the wordplay.
'layout' indicates an anagram (an alternative layout of the letters).
'learn' with letters rearranged gives 'RENAL'.
(Other definitions for renal that I've seen before include "Vital organ's" , "using the reins" , "around the kidney" , "Learn (anag) - of organs of the body" , "Concerning the kidneys" .)