Having worn corners (3-5)
'having worn corners' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for dog-eared that I've seen before include "Of book, with pages turned down at corners" , "Of book, with pages crumpled at the corners" , "Shabby with corners of pages turned down" , "(Of pages) having corners turned down or worn" , "Agree odd description of book with bent pages (3-5)" .)