Space traveller, tailed (5)
I believe the answer is:
comet
'space traveller' is the definition.
(object travelling through space)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for comet that I've seen before include "Tailed heavenly body" , "high-flier" , "Small extraterrestrial body" , "Line of rotation" , "traveller covering huge mileage" .)