One out of boredom penning English song (2,4)
I believe the answer is:
te deum
'song' is the definition.
(I know that Te Deum is a anthem)
I can't explain the rest of the clue.
(Other definitions for te deum that I've seen before include "Ancient Christian hymn" , "music" , "Christian hymn of thanksgiving" , "Church hymn" , "Early Christian hymn of praise to God (Latin)" .)