Each unfilled cake is behind a pastry dish
I believe the answer is:
apiece
'each' is the definition.
('apiece' can be a synonym of 'each')
'unfilled cake is behind a pastry dish' is the wordplay.
'unfilled cake' becomes 'ce' (I can't explain this - if you can you should believe this answer much more).
'is behind' is a charade indicator (letters next to each other).
'pastry dish' becomes 'pie' (I've seen this before).
'a'+'pie'='apie'
'ce' put after 'apie' is 'APIECE'.
Can you help me to learn more?
(Other definitions for apiece that I've seen before include "For or by each one of group" , "Per person" , "A head" , "for everyone" .)