How many letters does the top answer for “the hallucinatory alkaloid that is the active agent in mescal buttons” have?

The most common answer is mescaline (9 letters).

Crossword clue: the hallucinatory alkaloid that is the active agent in mescal buttons

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

mescaline 9 letters wn-def

the hallucinatory alkaloid that is the active agent in mescal buttons

peyote 6 letters wn-def

the hallucinatory alkaloid that is the active agent in mescal buttons