Genuine about name of the kidneys (5)
I believe the answer is:
renal
'of the kidneys' is the definition.
(I've seen this before)
'genuine about name' is the wordplay.
'genuine' becomes 'real' (associated in meaning).
'about' means one lot of letters goes inside another.
'name' becomes 'n' (common abbreviation e.g. on forms).
'real' enclosing 'n' is 'RENAL'.
(Other definitions for renal that I've seen before include "Vital organ's" , "associated with organ" , "using the reins" , "Pertaining to the kidney" , "Referring to organ" .)