Ultimately, voyager in space travelling remarkably long way (6)
I believe the answer is:
parsec
'long way' is the definition.
(I've seen this before)
'ultimately voyager in space travelling' is the wordplay.
'ultimately' says to take the final letters.
'travelling' is an anagram indicator.
The last letter of 'voyager' is 'r'.
'r'+'space'='rspace'
'rspace' anagrammed gives 'PARSEC'.
'remarkably' is the link.
This may not be right. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for parsec that I've seen before include "Large unit of distance" , "Enormous distance" , "Unit of astronomical length" , "it takes years to get this far" , "Unit of interstellar distance" .)