Assume someone's position or duties, especially in a satisfactory way. For example, It'll be hard to find someone to fill her shoes when she retires, or John expects his son to fill his shoes at the store. Also see in someone's shoes.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.