Possible Clues:

• This might be like a criminal to a pronounced extent
• First appearance of Hook or second in theatre
• Head of household
• This might make the snake cross to a pronounced extent
• Pronouncedly like a 9 across that might figure in a 24 across on a 19 across
• Something like 1 down, to a pronounced extent
• This might make the serpent cross to a pronounced extent
• Sounded with an H, like Hook
• A quarter quietly cross, being sound
• Sound made by bad-tempered snake?