Get allies upset and pass law (9)
I believe the answer is:
legislate
'pass law' is the definition.
(I've seen this before)
'get allies upset' is the wordplay.
'upset' indicates anagramming the letters.
'get'+'allies'='getallies'
'getallies' with letters rearranged gives 'LEGISLATE'.
'and' acts as a link.
(Other definitions for legislate that I've seen before include "Make rules" , "put in force" , "Pass through the house" , "Establish rules" , "discharge parliamentary business" .)