Best setter? (3,3)
I believe the answer is:
top dog
'best setter?' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'best setter?' is the wordplay.
'best' becomes 'top' (top can mean the very best).
'setter?' becomes 'dog' (a setter is a type of dog).
'top'+'dog'='TOP DOG'
Can you help me to learn more?
(Other definitions for top dog that I've seen before include "Dominant person" , "Not suitable" , "overall winner at Crufts" , "Member of learned society" , "Leading light (informal)" .)