A physical exercise (5-2)
I believe the answer is:
press-up
'a physical exercise' is the definition.
(I know that press-up is a type of arm exercise)
This is the entire clue.
(Other definitions for press-up that I've seen before include "Gymnastic floor exercise" , "Face-to-the-floor exercise" , "Form of arm exercise" , "Keep-fit exercise" , "Arm exercise while lying face down" .)