The most common and most likely answer to this crossword clue is the 8 letter word MISERERE
I've seen this crossword clue in Independent
M
I
S
E
R
E
R
E
More clues leading to the result MISERERE
- Pope’s Cotta, perhaps put on before psalm 51
- Parsimonious person before rendering penitential psalm
- Choir feature in tribute to prince HM backed repeatedly
- Fast way to understand king and queen being included in psalm
- Church music is covered by simple scripture lesson
- Piece of religious music from mass is before scripture class
- Rise unexpectedly in simple psalm
Buddy explains!

The straight part
We know that "psalm" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case psalm = miserere.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 MISERERE mean?
MISERERE noun- A prayer for mercy.
- An expression of lamentation or complaint.
- A medieval dagger, used for the mercy stroke to a wounded foe; misericord.
- A small projecting boss or bracket on the underside of the hinged seat of a church stall, intended to give some support to a standing worshipper when the seat is turned up; a misericord.
- Ileus.