How many letters does the top answer for “author of don quichotte” have?

The most common answer is massenet (8 letters).

Crossword clue: author of don quichotte

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

massenet 8 letters wd-fact-v3

French composer best remembered for his pop operas (1842-1912)

author of don carlos 50% similar → schiller

author of don juan 50% similar → byron

author of don quixote 50% similar → cervantes, petipa

composer of don quichotte 50% similar → massenet

wrote don quichotte 50% similar → massenet