Right-hand page in a directory (5)
I believe the answer is:
recto
'right-hand page' is the definition.
(right-hand page of a book)
'in a directory' is the wordplay.
'in' indicates a hidden word.
'RECTO' can be found hidden inside 'directory'.
(Other definitions for recto that I've seen before include "One page" , "one side" , "The right-hand page or leaf of a book" , "right page" , "Side of paper" .)