Girl in song at Christmas? (5)
I believe the answer is:
carol
This clue is a double definition.
'girl' is the first definition.
'song at christmas?' is the second definition.
'in' is the link.
(Other definitions for carol that I've seen before include "Female" , "sing happily" , "A traditional Christmas song or hymn" , "Song, especially at Christmas" , "Joyful religious song" .)