Cryptic crossword clue
Sunbeam best exploited in deep space

The most common and most likely answer to this crossword clue is the 11 letter word SUBBASEMENT

I've seen this crossword clue in Independent
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Buddy explains!

The straight part
We know that "deep space" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case deep space = subbasement.
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 SUBBASEMENT mean?

SUBBASEMENT noun
  1. A basement located beneath another basement

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