Song of starling starting in tree (5)
I believe the answer is:
psalm
'song' is the definition.
(I've seen this before)
'starling starting in tree' is the wordplay.
'starting' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'tree' becomes 'palm' (palm tree is a kind of tree**).
The initial letter of 'starling' is 's'.
's' inserted within 'palm' is 'PSALM'.
'of' acts as a link.
(Other definitions for psalm that I've seen before include "Old Testament lyrical poem or prayer" , "Palms (anag.)" , "Devotional song/hymn" , "What's heard in church" , "Sacred song of praise" .)