Delightful singing by chaps heading off (10)
I believe the answer is:
enchanting
'delightful' is the definition.
(thesaurus)
'singing by chaps heading off' is the wordplay.
'singing' becomes 'chanting' (chanting is a kind of singing**).
'by' says to put letters next to each other.
'chaps' becomes 'men' (I've seen this before).
'heading off' means to remove the first letter.
'men' with its initial letter removed is 'en'.
'chanting' put after 'en' is 'ENCHANTING'.
(Other definitions for enchanting that I've seen before include "Beguiling" , "occupation Circe undertook" , "Delightful" , "Charming" , "Lovely" .)