How many letters does the top answer for “a foot afflicted with a fallen arch; abnormally flattened and spread out” have?

The most common answer is flatfoot (8 letters).

Crossword clue: a foot afflicted with a fallen arch; abnormally flattened and spread out

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

flatfoot 8 letters wn-def

a foot afflicted with a fallen arch; abnormally flattened and spread out

splayfoot 9 letters wn-def

a foot afflicted with a fallen arch; abnormally flattened and spread out