Beautiful thing that's on the table at Christmas (7)
I believe the answer is:
cracker
I believe this clue is a double definition.
'beautiful thing' is the first definition.
'on the table at christmas' is the second definition.
'that's' is the link.
(Other definitions for cracker that I've seen before include "An outstanding example of its kind!" , "Xmas table extra" , "Christmas table item" , "Knockout biscuit?" , "Noisy firework" .)