A success at baseball (7)
I believe the answer is:
homerun
'baseball' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'a success' is the wordplay.
I cannot quite see how this works, but
'success' could be 'run' (run is a kind of success) and 'run' is present in the answer.
The remaining letters 'home' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'at' is the link.
Can you help me to learn more?
(Another definition for homerun that I've seen is " big hit in America".)