Condemn study on wild cat (8)
I believe the answer is:
'condemn' is the definition.
(I know that condemn is a more specific form of the action denounce)
'study on wild cat' is the wordplay.
'study' becomes 'den' (term for a study or office).
'on' means one lot of letters go next to another.
'wild cat' becomes 'ounce' (I've seen this before).
(Other definitions for denounce that I've seen before include "Openly deplore" , "Speak publicly or give information against" , "Openly condemn" , "Condemn or censure" , "Speak publicly against, expose" .)