How many letters does the top answer for “a garment worn below another.” have?

The most common answer is undergarment (12 letters).

Crossword clue: a garment worn below another.

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

undergarment 12 letters web-def

a garment worn under other garments

another word for below 50% similar → beneath

another word for garment 50% similar → apparel, clothe, garb