How many letters does the top answer for “a word having an acute accent on the penultimate syllable.” have?

The most common answer is paroxytone (10 letters).

Crossword clue: a word having an acute accent on the penultimate syllable.

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

paroxytone 10 letters web-def

word having stress or acute accent on the next to last syllable