Excitable person (7)
I believe the answer is:
hothead
'excitable person' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for hothead that I've seen before include "An impetuous person with warm cranium" , "maniac" , "Impetuous irresponsible person" , "Quick-tempered person" , "Person liable to get reckless impulses" .)