He plans to no good purpose (7)
I believe the answer is:
schemer
'he plans to no good purpose' 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 really see how this works, but
'he' could be 'che' and 'che' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for schemer that I've seen before include "one inventing plots" , "Devious type" , "Machiavellian type" , "Person who plots" , "He plots and plans" .)