Breeding area and what a stallion did there they say (4)

I believe the answer is:

stud

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'breeding' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for stud that I've seen before include "Small rounded earring" , "Lothario" , "Stallion kept for breeding" , "Removable collar button" , "Ladies' man?" .)

I've seen this clue in The Irish Times.

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