In good physical shape
I believe the answer is:
fit
'in good physical shape' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for fit that I've seen before include "Healthy, exercised" , "Adequate" , "'Sudden attack, of coughing say (3)'" , "Healthy; conform to" , "Suitable; sudden attack" .)