How many letters does the top answer for “located below or beneath something else” have?

The most common answer is nether (6 letters).

Crossword clue: located below or beneath something else

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

nether 6 letters wn-def

located below or beneath something else

under 5 letters wn-def

down to defeat, death, or ruin

that which is deposited beneath something else. 50% similar → subdeposit