The most common and most likely answer to this crossword clue is the 6 letter word DUPLEX
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More clues leading to the result DUPLEX
Buddy explains!

The straight part
We know that "Double" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case double = duplex.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 DUPLEX mean?
DUPLEX noun- A house made up of two dwelling units.
- A cancellation combining a numerical cancellation with a second mark showing time, date, and place of posting.
- A throwing motion where two balls are thrown with one hand at the same time.
- A double-stranded polynucleotide.
- A system of multiple thrust faults bounded above and below by a roof thrust and floor thrust.
- To make duplex.
- To make into a duplex.
- (juggling) To make a series of duplex throws.
- Double, made up of two parts.
- Bidirectional (in two directions).
- Having horizons with contrasting textures.