Rubbish ex-PM, creating upset (6)
I believe the answer is:
dismay
'upset' is the definition.
(dismay can mean to upset)
'rubbish ex-pm' is the wordplay.
'rubbish ex' becomes 'dis' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pm' becomes 'May' (former UK prime minister Theresa May).
'dis'+'may'='DISMAY'
'creating' acts as a link.
Can you help me to learn more?
(Other definitions for dismay that I've seen before include "Consternation, distress" , "Appal" , "Feeling of surprise and discouragement" , "Anxiety" , "Fill with consternation" .)