The most common and most likely answer to this crossword clue is the 8 letter word UNITISED
I've seen this crossword clue in The Guardian
U
N
I
T
I
S
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D
Buddy explains!
The straight part
We know that "turned into a single piece" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case turned into a single piece = unitised.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 UNITISED mean?
UNITISED verb- To manage as a unit
- To convert, package, or organize into one or more units