The ado he'd stirred up, being impetuous (9)
I believe the answer is:
hotheaded
'impetuous' is the definition.
('hotheaded' can be a synonym of 'impetuous')
'the ado he'd stirred up' is the wordplay.
'stirred up' indicates an anagram.
'the'+'ado'+'hed'='theadohed'
'theadohed' with letters rearranged gives 'HOTHEADED'.
'being' acts as a link.
(Other definitions for hotheaded that I've seen before include "Irresponsible" , "Explosive" , "rash" .)