Giving the girl a large book (6)
I believe the answer is:
missal
'book' is the definition.
(missal is a kind of book)
'giving the girl a large' is the wordplay.
'giving' says to put letters next to each other.
'the girl' becomes 'missa' (I can't explain this - if you can you should give a lot more credence to this answer).
'a large' becomes 'l'.
'missa' put next to 'l' is 'MISSAL'.
Can you help me to learn more?
(Other definitions for missal that I've seen before include "Religious book" , "Book used at Catholic mass" , "guide for the services" , "Prayer-book" , "Book used in RC Mass" .)