The most common and most likely answer to this crossword clue is the 7 letter word SINGING
I've seen this crossword clue in The Guardian
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More clues leading to the result SINGING
Buddy explains!

The straight part
We know that "chanting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case chanting = singing.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 SINGING mean?
SINGING verb- To produce musical or harmonious sounds with one’s voice.
- To express audibly by means of a harmonious vocalization.
- To soothe with singing.
- To confess under interrogation.
- To make a small, shrill sound.
- To relate in verse; to celebrate in poetry.
- To display fine qualities; to stand out as excellent.
- To be capable of being sung; to produce a certain effect by being sung.
- The act of using the voice to produce musical sounds; vocalizing.
- Disclosing information, or giving evidence about another.
- A gathering for the purpose of singing shape note songs.
- Smooth and flowing.
- (of a kettle etc.) Producing a whistling sound due to the escape of steam.