How many letters does the top answer for “a chemical used to kill insects” have?

The most common answer is insecticide (11 letters).

Crossword clue: a chemical used to kill insects

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

insecticide 11 letters wn-def

a chemical used to kill insects

a chemical agent used to kill mites 50% similar → acaricide

a chemical used to kill larval pests 50% similar → larvicide