How many letters does the top answer for “word having stress or acute accent on the antepenult” have?

The most common answer is proparoxytone (13 letters).

Crossword clue: word having stress or acute accent on the antepenult

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

proparoxytone 13 letters wn-def

word having stress or acute accent on the antepenult

a word which has the acute accent on the antepenult. 50% similar → proparoxytone