Chop up bird to make tart (5,3)
I believe the answer is:
mince pie
'tart' is the definition.
(I've seen this before)
'chop up bird' is the wordplay.
'chop up' becomes 'mince' (mincing is a kind of chopping up).
'bird' becomes 'pie' (sort of bird).
'mince'+'pie'='MINCE-PIE'
'to make' acts as a link.
(Other definitions for mince pie that I've seen before include "Xmas treat" , "Fruit-filled tart" , "Christmas fare" , "Festive pastry confection" , "Christmas delicacy" .)