Chief stud (4)

I believe the answer is:

boss

I believe this is a double definition.

'chief' is the first definition.
(synonyms)

'stud' is the second definition.
(synonyms)

(Other definitions for boss that I've seen before include "Behave overbearingly" , "Gaffer, manager" , "Master - stud" , "Stud; employer" , "Manager (colloq.); stud" .)

I've seen this clue in The Telegraph and The Guardian.

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