The most common and most likely answer to this crossword clue is the 6 letter word DONGLE
I've seen this crossword clue in Financial Times
D
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N
G
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More clues leading to the result DONGLE
Buddy explains!
The straight part
We know that "attachment to computer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case attachment to computer = dongle.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 DONGLE mean?
DONGLE noun- Any small device that plugs into an electronic device, typically a computer, and alters its functionality. Common examples include wireless modems, software copy protect devices, and adapters.
- A hardware device utilized by a specific application for purposes of copy protection.