How many letters does the top answer for “a russian measure of length containing 3,500 english feet.” have?

The most common answer is verst (5 letters).

Crossword clue: a russian measure of length containing 3,500 english feet.

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

verst 5 letters web-def

a Russian unit of length (1.067 km)