How many letters does the top answer for “author of old ideas” have?

The most common answer is cohen (5 letters).

Crossword clue: author of old ideas

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

cohen 5 letters wd-fact-v3

author of old school 50% similar → ferrell

author of the old capital 50% similar → kawabata

composer of old ideas 50% similar → cohen

wrote old ideas 50% similar → cohen