Book centre out for Christmas (4)
I believe the answer is:
noel
'christmas' is the definition.
('Noel' can be a synonym of 'christmas')
'book centre out' is the subsidiary indication.
'book' becomes 'novel' (novel is a kind of book).
'centre out' means to remove the middle letters.
'novel' with its centre taken out is 'noel'.
'for' is the link.
(Other definitions for noel that I've seen before include "Christmas time" , "Girl - boy - Christmas" , "Season around the 25th December" , "Another word for 7 Across" , "Xmas refrain" .)