One of three female monsters with live snakes for hair (6)
I believe the answer is:
gorgon
(Other definitions for gorgon that I've seen before include "In Greek myth, a snake-haired woman whose look turned people to stone" , "Medusa was one" , "(and 17) Italian cheese" , "Frightening woman" , "In Greek myth, a snake-haired woman whose look turned watcher to stone" .)