How many letters does the top answer for “having no cause or apparent cause” have?

The most common answer is causeless (9 letters).

Crossword clue: having no cause or apparent cause

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

causeless 9 letters wn-def

having no cause or apparent cause

uncaused 8 letters wn-def

having no cause or apparent cause

having no justifying cause or reason 50% similar → reasonless