The most common and most likely answer to this crossword clue is the 6 letter word PARSEC
P
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R
S
E
C
More clues leading to the result PARSEC
- To work out sentence, convict’s beginning a long stretch?
- Analyse speed of light, getting astronomical distance
- Critically analyse constant astronomical measurement
- Space rocket initially travelling an astronomically long way?
- Run between office assistants for quite a distance!
- Contrary forces rapidly covering a huge distance
- Advances rapidly westward, covering a great distance
- Copper locks up idiot for a very long stretch
- Voyager ultimately in space, flying an enormous distance
- Strike northward, dry for long distance
Buddy explains!

The straight part
We know that "astronomical distance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case astronomical distance = parsec.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PARSEC mean?
PARSEC noun- Parallax second