Alert, perceptive (2,3,4)
I believe the answer is:
on the ball
I believe this clue is a double definition.
'alert' is the first definition.
(on the ball can mean alert or paying attention)
'perceptive' is the second definition.
(thesaurus)
(Other definitions for on the ball that I've seen before include "Alert and practical - during soccer match?" , "like a balancing seal?" , "Alertly responsive" , "Alert to new ideas" , "Ready to take initiative" .)