Song gets stuck initially in tree (5)
I believe the answer is:
psalm
'song' is the definition.
(I've seen this before)
'stuck initially in tree' is the wordplay.
'initially' indicates taking the first letters.
'in' is an insertion indicator.
'tree' becomes 'palm' (palm tree is a kind of tree).
The first letter of 'stuck' is 's'.
's' placed into 'palm' is 'PSALM'.
'gets' acts as a link.
(Other definitions for psalm that I've seen before include "Lamps for a sacred song" , "Song - hymn - prayer" , "Church song" , "Song of David" , "What's heard in church" .)