How many letters does the top answer for “wrote all that jazz” have?

The most common answer is fosse (5 letters).

Crossword clue: wrote all that jazz

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

fosse 5 letters wd-fact-v3

ditch dug as a fortification and usually filled with water

wrote jazz 67% similar → morrison

author of all that jazz 50% similar → fosse

director of all that jazz 50% similar → fosse