Jet set finally gets to Mars (6)
I believe the answer is:
planet
'mars' is the definition.
(thesaurus)
'jet set finally' is the wordplay.
'jet' becomes 'plane'.
'finally' suggests the final letters.
The last letter of 'set' is 't'.
'plane'+'t'='PLANET'
'gets to' is the link.
(Other definitions for planet that I've seen before include "Mars or Uranus" , "Orbiting body in the heavens" , "Orbiting heavenly body" , "Large satellite of star" , "one of seven in suite" .)