How many letters does the top answer for “wrote to kill a mockingbird” have?

The most common answer is lee (3 letters).

Crossword clue: wrote to kill a mockingbird

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

lee 3 letters wd-fact-v3

the side of something that is sheltered from the wind

author of to kill a mockingbird 50% similar → lee

wrote a view to a kill 50% similar → walken

wrote dressed to kill 50% similar → palma