Doctor can upset agreement (9)
I believe the answer is:
concordat
'agreement' is the definition.
(concordat is a kind of agreement)
'doctor can upset' is the wordplay.
'upset' indicates anagramming the letters.
'doctor'+'can'='doctorcan'
'doctorcan' anagrammed gives 'CONCORDAT'.
(Other definitions for concordat that I've seen before include "Agreement with Rome" , "Signed agreement" , "pact" , "papal blessing" .)