The most common and most likely answer to this crossword clue is the 11 letter word ACQUISITION
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Buddy explains!

The straight part
We know that "/ / /Purchase" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case / / /purchase = acquisition.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 ACQUISITION mean?
ACQUISITION noun- The act or process of acquiring.
- The thing acquired or gained; a gain.
- The process of sampling signals that measure real world physical conditions and converting these signals into digital numeric values that can be manipulated by a computer.