Earth maybe from track used in exercise (6)
I believe the answer is:
planet
'earth maybe' is the definition.
(Earth is an example)
'track used in exercise' is the wordplay.
'track' becomes 'lane'.
'used in' indicates putting letters inside.
'exercise' becomes 'PT' (Physical Training).
'lane' inserted into 'pt' is 'PLANET'.
'from' is the link.
(Other definitions for planet that I've seen before include "Jupiter is one" , "body in orbit" , "Eg, Mars or Pluto" , "Neptune, for example" , "Venus, for example" .)