Possible Clues:

• It's a measure of what's discovered in Martin Chuzzlewit
• Twelfth of foot
• Move gradually a little distance from Wexford
• 'In Galway, ball in ah with it, for a core of Dublin (4)'
• Scottish and Irish word for an island
• Advance slowly under His roof?
• She led the Iceni; bade ciao (anag.)
• In church, to start with, in short (4)
• Long Island? Hardly
• Kind of worm