How many letters does the top answer for “farm machine that gathers a food crop from the fields” have?

The most common answer is harvester (9 letters).

Crossword clue: farm machine that gathers a food crop from the fields

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

harvester 9 letters wn-def

farm machine that gathers a food crop from the fields

reaper 6 letters wn-def

farm machine that gathers a food crop from the fields