The most common and most likely answer to this crossword clue is the 8 letter word ASTEROID
I've seen this crossword clue in The Times
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More clues leading to the result ASTEROID
- A body builder’s out-of-this-world body
- For exercise, rides to a distant rock
- An enhancing drug for heavenly body
- A distant body, Daisy has no way to prove who she is
- Sit and adore rippling body
- A chemical weightlifters might try to get a heavenly body
- Modified radio set for space orbiter
- Single muscle developer’s heavenly body
- A bodybuilder – one's out of this world!
- Daisy with instinctive drive to orbit round minor planet
Buddy explains!

The straight part
We know that "a heavenly body" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a heavenly body = asteroid.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 ASTEROID mean?
ASTEROID noun- Any member of the taxonomic class Asteroidea; a starfish
- A naturally occurring solid object, which is smaller than a planet and is not a comet, that orbits a star
- In the Solar system, such a body that orbits within the orbit of Jupiter