Game bird stuffed with proper cooking apples, originally (6)
I believe the answer is:
tipcat
'game' is the definition.
(I've seen this before)
'bird stuffed with proper cooking apples originally' is the wordplay.
'bird' becomes 'tit' (I've seen this before**).
'stuffed with' indicates putting letters inside (I've seen this in other clues).
'originally' suggests taking the first letters.
The first letters of 'proper cooking apples' is 'pca'.
'tit' going around 'pca' is 'TIPCAT'.
(Other definitions for tipcat that I've seen before include "Game" , "Hint" .)