Song and dance among endless Christmas turns (7)
I believe the answer is:
lullaby
'song' is the definition.
(lullaby is a kind of song)
'dance among endless christmas turns' is the wordplay.
'dance' becomes 'ball' (ball is a kind of dance).
'among' is an insertion indicator.
'endless' means to remove the last letter.
'christmas' becomes 'yule' (Yule is the Christmas period).
'turns' says the letters should be written backwards.
'yule' with its final letter removed is 'yul'.
'ball' going within 'yul' is 'yballul'.
'yballul' back-to-front is 'LULLABY'.
'and' acts as a link.
(Other definitions for lullaby that I've seen before include "Song to send one to sleep" , "Cradle song" , "composition" , "Sleep-inducing song" , "Go-to-sleep song" .)