The most common and most likely answer to this crossword clue is the 7 letter word OPAQUER
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More clues leading to the result OPAQUER
Buddy explains!

The straight part
We know that "less transparent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case less transparent = opaquer.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 OPAQUER mean?
OPAQUER adjective- Neither reflecting nor emitting light.
- Allowing little light to pass through, not translucent or transparent.
- Unclear, unintelligible, hard to get or explain the meaning of
- Obtuse, stupid.
- Describes a type for which higher-level callers have no knowledge of data values or their representations; all operations are carried out by the type's defined abstract operators.