Silly problem making Chinese food (3,3)

I believe the answer is:

dim sum

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But I can't explain it at all! Could you help me understand?

(Other definitions for dim sum that I've seen before include "Chinese dumpling dish" , "Chinese course" , "Failure of mathematician, possibly" , "Selection of Chinese foods as appetizer" , "parcels from China" .)

I've seen this clue in The Irish Times.

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