Husband's rottenness stirred up hostile reaction (7,4)

I believe the answer is:

hornets nest

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'up hostile reaction' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'husband's rottenness stirred' is the wordplay.
'husband' becomes 'h'.
'stirred' indicates an anagram.
'rottenness' anagrammed gives 'ornetsnest'.
'h'+'ornetsnest'='HORNETS NEST'

Can you help me to learn more?

(Other definitions for hornets nest that I've seen before include "Something not to be stirred up" , "Stirred up it's dangerous" , "(Stir up a) violent reaction" , "Big trouble!" , "hazardous situation" .)

I've seen this clue in The Independent.

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