A victor breaks record, winning tennis tournament (5,3)
I believe the answer is:
davis cup
'tennis tournament' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for davis cup that I've seen before include "International tennis tournament" , "International lawn tennis championship" , "event?" , "International tennis team championship" , "Sets competition" .)