The most common and most likely answer to this crossword clue is the 3 plus 5 letter word AVE MARIA
I've seen this crossword clue in Independent
A
V
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M
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A
More clues leading to the result AVE MARIA
- A very English mass song/prayer
- Prayer girl elevated mass with melodic piece
- A very English mass, with song and prayer
- On tree-lined road Frau von Trapp offers prayer
- Salutation to a virgin maiden enthralled by Cockney’s own song
- Prayer books changing non- Conservative America
- Mexican musician ignoring cold welcome next door to street’s spiritual address
- Prayer song after a verse to accompany English mass
- Ecclesiastical passage, a thoroughfare taken by lady
- Verse by Forster used in a song and a prayer
Buddy explains!

The straight part
We know that "prayer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case prayer = ave maria.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.