Song is able to delight passing king (8)
I believe the answer is:
canticle
'song' is the definition.
(I have seen 'Liturgical song ' mean 'canticle' so perhaps 'song' could also mean 'canticle')
'able to delight passing king' is the wordplay.
I cannot really see how this works, but
'able' could be 'can' and 'can' is present in the answer.
This may be the basis of clue (or it may be nonsense).
'is' acts as a link.
Can you help me to learn more?
(Other definitions for canticle that I've seen before include "is heard in church" , "Liturgical song" , "A religious song" , "Short hymn" , "Church hymn or chant" .)