The most common and most likely answer to this crossword clue is the 15 letter word ONE-DIMENSIONAL
I've seen this crossword clue in The Times
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More clues leading to the result ONE-DIMENSIONAL
Buddy explains!
The straight part
We know that "Unsophisticated" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unsophisticated = one-dimensional.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 ONE-DIMENSIONAL mean?
ONE-DIMENSIONAL adjective- Having length, but no width, height or depth.
- Lacking depth or believability; flat.
- Lacking personal depth and substance; conceited, vain, shallow, superficial (see also; two-dimensional).