The most common and most likely answer to this crossword clue is the 9 letter word HIERARCHS
I've seen this crossword clue in The Times
H
I
E
R
A
R
C
H
S
Buddy explains!
The straight part
We know that "blessed rulers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case blessed rulers = hierarchs.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 HIERARCHS mean?
HIERARCHS noun- One who has high and controlling authority in sacred things; the chief of a sacred order.
- A title of bishops in their role as ordinaries (arbiters of canon law) over their respective dioceses.