The most common and most likely answer to this crossword clue is the 12 letter word UNAUTHORISED
I've seen this crossword clue in The Daily Telegraph
U
N
A
U
T
H
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D
More clues leading to the result UNAUTHORISED
Buddy explains!
The straight part
We know that "Like certain biographies" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case like certain biographies = unauthorised.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 UNAUTHORISED mean?
UNAUTHORISED adjective- Not authorised; having no authority.