Free book prefaces with a line of The Woman in White? (6)
I believe the answer is:
bridal
'the woman in white?' is the definition.
(I've seen this before)
'free book prefaces with a line' is the wordplay.
'free' becomes 'rid' (to be free of something is to be rid of it).
'book' becomes 'b' (abbreviation for book).
'prefaces' is a charade indicator (letters next to each other) (some letters go before others).
'with' is a charade indicator (letters next to each other).
'line' becomes 'l' (used when specifying particular lines from a poem).
'rid' put after 'b' is 'brid'.
'brid'+'a'+'l'='BRIDAL'
'of' is the link.
(Other definitions for bridal that I've seen before include "Relating to the woman getting married" , "Woman in White" , "Newly-wed" , "Wedding's" , "To do with wedding - perhaps a suite" .)