Related Clues:

• Hold back or set aside for future use
• Reserve, taciturnity
• Put aside for special use
• 'Reserve, taciturnity (9)'
• Retain for future use
• Book to act once more like a 25 down, perhaps
• What 16 across may do once more by the book?
• That's the way to be a waiter again, but keep it to yourself
• The twelfth man
• There's little give in this, in a manner of speaking
• It's Timothy that I tidy because of his shyness
• Wait again, perhaps, and do it by the book
• This book will work to be a waiter once more, it seems
• This might bring one to book for keeps
• Do it by the book?