Related Clues:

• This old mum is taking the place of one
• App tappers
• "Tank Engine" of kid-lit
• Apostle who doubted
• Patron Saint of people in doubt
• Supreme Court Justice Clarence ___
• Scarily, T-shirt conceals rejected needles
• Rev W Awdry’s tank engine
• Marshall's successor on the Supreme Court
• Doubting one
• 'A Child's Christmas in Wales' poet
• *See 35-Across
• Name Gray had for Welsh poet
• Sharp pens?
• Every so often, mislay stash brought up for engravers