Impulsive type, he had to elaborate (7)
I believe the answer is:
hothead
'impulsive type' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'he had to elaborate' is the wordplay.
'elaborate' indicates anagramming the letters (an elaborate version of the letters).
'he'+'had'+'to'='hehadto'
'hehadto' anagrammed gives 'HOTHEAD'.
Can you help me to learn more?
(Other definitions for hothead that I've seen before include "Excitable person" , "Impulsive person" , "Headstrong type" , "Tearaway" , "Daredevil" .)