The most common and most likely answer to this crossword clue is the 11 letter word LIBERTICIDE
L
I
B
E
R
T
I
C
I
D
E
Buddy explains!
The straight part
We know that "destroyer of freedom" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case destroyer of freedom = liberticide.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.