Song of the tree around the end of Christmas (5)
I believe the answer is:
psalm
'song' is the definition.
(I've seen this before)
'the tree around the end of christmas' is the wordplay.
'the tree' becomes 'palm' (palm is a kind of tree**).
'around' indicates putting letters inside.
'the end of' suggests the final letters.
The final letter of 'christmas' is 's'.
'palm' enclosing 's' is 'PSALM'.
'of' is the link.
(Other definitions for psalm that I've seen before include "Sacred song of praise" , "Song of David" , "Jewish hymn" , "Church song" , "What's heard in church" .)