The most common and most likely answer to this crossword clue is the 3 plus 5 plus 6 letter word THE LORDS SUPPER
I've seen this crossword clue in Financial Times
T
H
E
L
O
R
D
S
S
U
P
P
E
R
Buddy explains!
The straight part
We know that "holy meal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case holy meal = the lords supper.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.