Palms off a song (5)
I believe the answer is:
psalm
'a song' is the definition.
(I've seen this before)
'palms off' is the wordplay.
'off' indicates an anagram.
'palms' with letters rearranged gives 'PSALM'.
(Other definitions for psalm that I've seen before include "Old Testament hymn" , "OT hymn" , "Jewish hymn" , "A song which praises" , "Song - hymn - prayer" .)