Book I've unwrapped in the middle of Christmas (5)
I believe the answer is:
'book' is the definition.
(I know that novel is a type of book)
'i've unwrapped in the middle of christmas' is the wordplay.
'unwrapped' says to take the centre (the letters which wrap the word are removed).
'in the middle of' is an insertion indicator.
'christmas' becomes 'Noel' (Noel can mean Christmas).
The middle of 'ive' is 'v'.
'v' inserted within 'noel' is 'NOVEL'.
(Other definitions for novel that I've seen before include "Interestingly new; book" , "Fresh" , "She, for example" , "Rebecca?" , "Innovative" .)