How many letters does the top answer for “a linear unit of length equal to 12 inches or a third of a yard” have?

The most common answer is ft (2 letters).

Crossword clue: a linear unit of length equal to 12 inches or a third of a yard

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

ft 2 letters wn-def

a linear unit of length equal to 12 inches or a third of a yard

a unit of length equal to 220 yards 57% similar → furlong