Possible Clues:

• Sounds as if H makes the serpent 31 across
• H is like a buccaneer
• This might make one as mad as a snake to a pronounced extent
• Breathed consonant
• Pronouncedly like a danger overseas
• Start with an H, like Hook, perhaps
• Don't drop ones aitches like Captain 'ook, say
• Stop making reptile cross
• This makes the serpent cross to a pronounced extent
• Like a criminal to a pronounced degree