How many letters does the top answer for “the act of extinguishing; causing to stop burning” have?

The most common answer is extinction (10 letters).

Crossword clue: the act of extinguishing; causing to stop burning

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

extinction 10 letters wn-def

the act of extinguishing; causing to stop burning

quenching 9 letters wn-def

the act of extinguishing; causing to stop burning