Working to block protest against end of city state (8)
I believe the answer is:
monarchy
'state' is the definition.
(I have seen 'Sovereign state ' mean 'monarchy' so perhaps 'state' could also mean 'monarchy')
'working to block protest against end of city' is the wordplay.
'working' becomes 'on' (on can mean working or activated).
'to block' indicates putting letters inside (block can mean to fill a hole in something).
'protest against' becomes 'march' (I can't explain this - if you can you should give a lot more credence to this answer).
'end of' suggests the final letters.
The final letter of 'city' is 'y'.
'on' going within 'march' is 'monarch'.
'monarch'+'y'='MONARCHY'
Can you help me to learn more?
(Other definitions for monarchy that I've seen before include "Sovereign state" , "Rule by a king or queen" , "kind of government" , "realm" , "Kingdom - kingship" .)