Old film star's talk that's hard to follow without a book (5)
I believe the answer is:
gable
'old film star's' is the definition.
(Clark Gable, 1901-1960)
'talk that's hard to follow without a book' is the wordplay.
'talk that's hard to follow' becomes 'gabble' (gabble can mean unintelligible talk).
'without' is a deletion indicator.
'a book' becomes 'b' (abbreviation for book).
'gabble' with 'b' taken out is 'GABLE'.
(Other definitions for gable that I've seen before include "See 18" , "Part of house" , "Section of wall between roof slopes" , "Triangular upper part of a wall under a roof" , "Side of house or Clark, film star" .)