Starts to take seriously appalling Russian despot (4)
I believe the answer is:
tsar
'despot' is the definition.
(I've seen this before)
'starts to take seriously appalling russian' is the wordplay.
'starts to' says to take the initial letters.
The initial letters of 'take seriously appalling russian' is 'TSAR'.
(Other definitions for tsar that I've seen before include "specific authority" , "One associated with 26 [KREMLIN]" , "Eg, Ivan the Terrible" , "Russian leader" , "Title of Russian emperor" .)