Taking advice is not what he needs! (12)
I believe the answer is:
kleptomaniac
'taking advice is not what he needs' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'not what he needs' is the wordplay.
I cannot really see how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
'he' could be 'man' (I've seen this in another clue) and 'man' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for kleptomaniac that I've seen before include "A man to pickle (anag) - one with an urge to steal" , "Compulsive thief" , "Motiveless thief" , "Obsessive thief" .)