The most common and most likely answer to this crossword clue is the 13 letter word AUTHORITARIAN
I've seen this crossword clue in The Times
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More clues leading to the result AUTHORITARIAN
Buddy explains!

The straight part
We know that "despotic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case despotic = authoritarian.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does AUTHORITARIAN mean?
AUTHORITARIAN noun- One who commands absolute obedience to his or her authority.
- One who follows and is excessively obedient to authority.
- Of, or relating to, or exhibiting strict obedience to an authority; favoring authoritarianism over civic and individual liberties.
- Demanding obedience to authority; marked by authoritarianism; dictatorial, tyrannical.
- Tending to impose one's demands upon others as if one were an authority.