How many letters does the top answer for “a unit of apothecary weight equal to 480 grains or one twelfth of a troy pound” have?

The most common answer is ounce (5 letters).

Crossword clue: a unit of apothecary weight equal to 480 grains or one twelfth of a troy pound

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

ounce 5 letters wn-def

a unit of apothecary weight equal to 480 grains or one twelfth of a troy pound

a unit of apothecary weight equal to 24 grains 56% similar → pennyweight