For each expert, a pastry dish is brought in (6)
I believe the answer is:
apiece
'for each' is the definition.
('apiece' can be a synonym of 'each')
'expert a pastry dish is brought in' is the wordplay.
'expert' becomes 'ace' (ace is a kind of expert).
'a pastry dish' becomes 'pie' (I've seen this before).
'is brought in' is an insertion indicator.
'ace' placed around 'pie' is 'APIECE'.
(Other definitions for apiece that I've seen before include "For or by each one of group" , "A head" , "for everyone" , "Per person" .)