The most common and most likely answer to this crossword clue is the 9 letter word DIACONATE
I've seen this crossword clue in The Daily Telegraph
D
I
A
C
O
N
A
T
E
Buddy explains!
The straight part
We know that "clerical office" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case clerical office = diaconate.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 DIACONATE mean?
DIACONATE noun- The rank of a deacon.
- Deacons considered as a group; a body or board of deacons.
- The period of office of a deacon.