Intrinsic adrenalin is relating to kidneys (5)
I believe the answer is:
renal
'relating to kidneys' is the definition.
(I've seen this before)
'intrinsic adrenalin' is the wordplay.
'RENAL' is hidden in amongst the letters.
However, I'm not sure how this is indicated.
'is' is the link.
Can you help me to learn more?
(Other definitions for renal that I've seen before include "Like an organ" , "connected with organ" , "Pertaining to the kidneys" , "Relating to kidneys" , "Referring to organ" .)