Caesar upset representative in his city (7)
I believe the answer is:
emperor
'caesar' is the definition.
(I've seen this in another clue)
'upset representative in his city' is the wordplay.
'upset' shows that the letters should be reversed in order.
'representative' becomes 'rep' (rep is a kind of representative).
'in' is an insertion indicator.
'his city' becomes 'rome' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rep' inserted within 'rome' is 'rorepme'.
'rorepme' reversed gives 'EMPEROR'.
Can you help me to learn more?
(Other definitions for emperor that I've seen before include "Roman leader" , "Ruler of large territory" , "Absolute ruler" , "Purple --; -- penguin" , "Japanese version of the king" .)