How many letters does the top answer for “composer of the five days” have?

The most common answer is argento (7 letters).

Crossword clue: composer of the five days

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

argento 7 letters wd-fact-v3

author of the five days 50% similar → argento

composer of night and day 50% similar → porter

composer of the remains of the day 50% similar → ishiguro

wrote the five days 50% similar → argento