How many letters does the top answer for “a bed of oysters or mussels.” have?

The most common answer is scalp (5 letters).

Crossword clue: a bed of oysters or mussels.

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

scalp 5 letters web-def

the skin that covers the top of the head