Some uprising from Caesar, a stonking emperor! (4)
I believe the answer is:
tsar
'emperor' is the definition.
(I've seen this before)
'some uprising from caesar a stonking' is the wordplay.
'some uprising' says the letters should be written in reverse.
'from' says the answer is hidden in the clue.
'rast' is hidden in the letters of 'caesar a stonking'.
'rast' backwards is 'TSAR'.
(Other definitions for tsar that I've seen before include "Absolute ruler" , "Eg, Ivan the Terrible" , "Powerful man" , "Monarch of old Russia" , "Supremo" .)