The most common and most likely answer to this crossword clue is the 9 letter word PLAUSIBLE
P
L
A
U
S
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B
L
E
More clues leading to the result PLAUSIBLE
- Glib learner in pub is transformed with ale
- Silver-tongued Conservative leaving badly organised public sale
- Likely a blue slip will require alterations
- Convincing bonus involving a collection of 7 with no beginning
- Reasonable advantage retaining a religious work originally lost
- Ruination of all independent English pubs is likely
- Likely complication of pill abuse
- Smooth operator taking one in – I’ll find belief in odd places
- Appalling pill abuse that might occur
Buddy explains!

The straight part
We know that "Reasonable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reasonable = plausible.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 PLAUSIBLE mean?
PLAUSIBLE adjective- Seemingly or apparently valid, likely, or acceptable; conceivably true or likely
- Obtaining approbation; specifically pleasing; apparently right; specious.
- Worthy of being applauded; praiseworthy; commendable; ready.