How many letters does the top answer for “a verse or song to be chanted or sung in response” have?

The most common answer is antiphon (8 letters).

Crossword clue: a verse or song to be chanted or sung in response

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

antiphon 8 letters wn-def

a verse or song to be chanted or sung in response

antiphony 9 letters wn-def

a verse or song to be chanted or sung in response