Scores 100% on (4)
I believe the answer is:
aces
'scores 100% on' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aces that I've seen before include "Unreturnable services" , "Expert fliers" , "Winning serves" , "Case of top cards" , "They're high and low on cards" .)