He can't help helping himself (12)
I believe the answer is:
kleptomaniac
'he can't help helping himself' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he' is the wordplay.
I cannot quite see how this works, but
'he' could be 'tom' (I've seen this in another clue) and 'tom' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for kleptomaniac that I've seen before include "Motiveless thief" , "Obsessive thief" , "Compulsive thief" , "A man to pickle (anag) - one with an urge to steal" .)