Cake from leavened grain with half fat stuffing (6)

I believe the answer is:

eclair

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'cake' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for eclair that I've seen before include "Comedienne" , "Cream bun" , "Long chocolate cake for Claire" , "Choux pastry cream cake" , "Food" .)

I've seen this clue in The Telegraph.

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