The most common and most likely answer to this crossword clue is the 5 letter word COMET
I've seen this crossword clue in The Times
C
O
M
E
T
More clues leading to the result COMET
- Space traveller wasn’t the only one to get in contact?
- Company gathered together to find astronomical object
- Long-distance traveller from Maine sleeping like a baby?
- Celestial visitor has to arrive on time
- Arrive on time in old plane
- Soldier in charge encountered traveller in space
- Reindeer not quite awake
- Astronomical phenomenon to arrive on time
- Traveller round sun bed the writer occupies
- Orbiting body has to arrive on time
Buddy explains!

The straight part
We know that "Reindeer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reindeer = comet.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 COMET mean?
COMET noun- A celestial body consisting mainly of ice, dust and gas in a (usually very eccentric) orbit around the Sun and having a "tail" of matter blown back from it by the solar wind as it approaches the Sun.
- A celestial phenomenon with the appearance given by the orbiting celestial body.
- Any of several species of hummingbird found in the Andes.