Ace of diamonds? (4,3)
I believe the answer is:
home run
'ace of diamonds?' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?
This is all the clue.
Can you help me to learn more?
(Other definitions for home run that I've seen before include "Achievement by a sporting all-rounder" , "Baseball hit allowing complete circuit to batter" , "Good baseball hit" , "In baseball, it allows batter to move through all bases" , "Baseball achievement" .)