Is his rottenness a bit academic? (3)
I believe the answer is:
cad
'is his rottenness' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a bit academic?' is the wordplay.
'a bit' indicates the answer is hidden within the clue (I've seen 'bit of' mean this).
'CAD' is hidden in the letters of 'academic'.
Can you help me to learn more?
(Other definitions for cad that I've seen before include "he's no gent" , "Ungentlemanly person" , "Bounder, scoundrel" , "Heel" , "That ain't no gentleman" .)