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

The straight part
We know that "Quibbler" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case quibbler = casuist.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 CASUIST mean?
CASUIST noun- A person who resolves cases of conscience or moral duty.
- Someone who attempts to specify exact and precise rules for the direction of every circumstance of behaviour.
- One who is skilled in, or given to, casuistry.