Space traveller has a heavenly body (5)
I believe the answer is:
comet
This clue is a double definition.
'space traveller' is the first definition.
(I've seen this before)
'a heavenly body' is the second definition.
(comet is a kind of heavenly body)
'has' is the link.
(Other definitions for comet that I've seen before include "astronomical sight" , "High-flyer" , "Object in space with bright centre and long hazy tail" , "One is named after Edmond Halley" , "Tailed space traveller" .)