Sounded thrilled to have escaped, gradually having change of heart (5)

I believe the answer is:

oohed

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

I cannot understand how the rest of the clue works.

(Other definitions for oohed that I've seen before include "showed pleasure" , "Sounded thrilled" .)

I've seen this clue in The Times.

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