Excitable, paint from the mind (13)
I believe the answer is:
temperamental
'excitable' is the definition.
(thesaurus)
'paint from the mind' is the wordplay.
'paint' becomes 'tempera' (type of paint).
'from' is a charade indicator (letters next to each other).
'the mind' becomes 'mental' (I can't justify this - if you can you should believe this answer much more).
'tempera'+'mental'='TEMPERAMENTAL'
Can you help me to learn more?
(Other definitions for temperamental that I've seen before include "Moody, sensitive" , "Liable to changes of mood" , "Subject to sharply varying moods" , "requiring delicate handling" , "Likely to act unpredictably" .)