The most common and most likely answer to this crossword clue is the 6 letter word ALLEGE
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More clues leading to the result ALLEGE
- Claim covered by local legend
- Assert without proof everyone European has good English
- Claim posh girl backtracks in drink
- Claim member pitched into porter, say
- Claim everything, say, and concede in the end
- A place of learning has no business making claim
- Claim, for instance, the French almost go around
- Claim litre, say, in drink
- Claim supporter tucked into the booze
- Without basis claim supporter’s overcome by beer
Buddy explains!

The straight part
We know that "Maintain" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case maintain = allege.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 ALLEGE mean?
ALLEGE verb- To state under oath, to plead.
- To cite or quote an author or his work for or against.
- To adduce (something) as a reason, excuse, support etc.
- To make a claim as justification or proof; to make an assertion without proof.
- To lighten, diminish.