___ monster (only venomous lizard native to the U.S.)

GILA

This slow-moving desert dweller shares its name with an Arizona river.

This clue fills in the blank for a venomous lizard found only in the southwestern U.S., specifically the Gila monster. The name "Gila" (pronounced HEE-luh) comes from the Gila River basin where it’s commonly found. There’s no wordplay here—it’s a straightforward fact-based clue pointing to the only native venomous lizard in America.