How many letters does the top answer for “to make smooth and flowing, as a vessel's lines.” have?

The most common answer is fair (4 letters).

Crossword clue: to make smooth and flowing, as a vessel's lines.

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

fair 4 letters web-def

free from favoritism or self-interest or bias or deception; conforming with established standards or rules