The most common and most likely answer to this crossword clue is the 3 plus 2 plus 7 letter word ACT OF WORSHIP
A
C
T
O
F
W
O
R
S
H
I
P
Buddy explains!
The straight part
We know that "liturgy, say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case liturgy, say = act of worship.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.