Waste processor's name set in concrete (5)
I believe the answer is:
renal
'waste processor's' is the definition.
Although both the answer and definition are adjectives, I don't understand how one could define the other.
'name set in concrete' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'set in' means one lot of letters goes inside another.
'concrete' becomes 'real' (associated in meaning).
'n' inserted into 'real' is 'RENAL'.
(Other definitions for renal that I've seen before include "Concerning the kidneys" , "Learn (anag) - of organs of the body" , "associated with organ" , "around the kidney" , "Pertaining to the kidney" .)