He is trained to come up with constructive ideas (9)
I believe the answer is:
architect
'he is trained to come up with constructive ideas' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he is' is the wordplay.
I cannot quite see how this works, but
'he' could be 'arch' and 'arch' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for architect that I've seen before include "Wren perhaps" , "professional" , "Building designer" , "Designer of buildings" , "Perhaps Scott" .)