How many letters does the top answer for “a vehicle with a single wheel that is driven by pedals” have?

The most common answer is monocycle (9 letters).

Crossword clue: a vehicle with a single wheel that is driven by pedals

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

monocycle 9 letters wn-def

a vehicle with a single wheel that is driven by pedals

unicycle 8 letters wn-def

a vehicle with a single wheel that is driven by pedals