Happened to be the person commanding a dog, like a setter (8)
I believe the answer is:
occurred
'happened' is the definition.
('occur' can be a synonym of 'happen')
'like a setter' is the wordplay.
'like a' becomes 'occur' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'setter' becomes 'red' (red setter is a kind of setter).
'occur'+'red'='OCCURRED'
'to be the person commanding a dog' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for occurred that I've seen before include "Took place" , "Happened" , "Came to pass" .)