Tyrant famous soprano knocked back (4)
I believe the answer is:
tsar
'tyrant' is the definition.
(I've seen this before)
'famous soprano knocked back' is the wordplay.
I cannot quite see how this works, but
'soprano' could be 's' (musical abbreviation) and 's' is present in the answer.
The remaining letters 'tar' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tsar that I've seen before include "Despot" , "Rats to the Russian emperor" , "Title given to the kings of Bulgaria" , "Supreme authority" , "Formal rulings on Islamic law; was aft (anag.)" .)