The most common and most likely answer to this crossword clue is the 8 letter word SPACEMAN
I've seen this crossword clue in The Daily Telegraph
S
P
A
C
E
M
A
N
More clues leading to the result SPACEMAN
- Astronaut on reflection best among the stars
- Celebrity outdoes returning long-distance traveller
- Small fast bowler one rocket-propelled
- Call back to find odds on Bill becoming an astronaut
- Second fast bowler, one rocket-propelled?
- Pointless friend losing head and gathering speed for Armstrong, perhaps?
- Second bowler? He’s out of this world
- Advertising agent who’s out-of-this-world?
- Getting kiss finally, quickie, one’s off on a long journey
- Astronaut’s monicker is better read backwards!
Buddy explains!

The straight part
We know that "Armstrong, perhaps?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case armstrong, perhaps? = spaceman.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 SPACEMAN mean?
SPACEMAN noun- An astronaut, often a male astronaut.