Possible Clues:

• No P back there around 21 across makes it very largely long
• Tropical non-venomous snake
• Japanese drama character mostly recalled as a crawler
• No, the P can be made into a wraparound
• Boa you wouldn't want around your neck!
• Slithery sort outwardly pretty though overblown
• Slithering constrictor
• Snake (called Monty?)
• Programming language that's good at compression?
• Horribly hard time with pony and serpent