Observe derisory response not engaging all hearts (5)

I believe the answer is:

catch

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'hearts' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps there's an association between them I don't understand?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for catch that I've seen before include "Hidden problem; trap" , "potential partner?" , "Intercept and hold" , "Hidden drawback" , "Seize; start burning" .)

I've seen this clue in The Independent.

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