It may get upset over trifles (7)

I believe the answer is:

custard

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'it may get upset over trifles' is the definition.
The definition suggests a singular noun which matches the answer.

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(Other definitions for custard that I've seen before include "Yellow mixture" , "Egg/milk bake" , "Sweet sauce made with milk and eggs" , "Yellow sauce" , "Dessert sauce" .)

I've seen this clue in The Sun and The Globe and Mail.

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