The most common and most likely answer to this crossword clue is the 6 letter word JEJUNE
I've seen this crossword clue in Financial Times
J
E
J
U
N
E
Buddy explains!
The straight part
We know that "acking sophistication" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case acking sophistication = jejune.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 JEJUNE mean?
JEJUNE adjective- (now rare) Not nutritious.
- (by extension, of a speech or an argument) Lacking matter; empty; devoid of substance.
- Naive; simplistic.