The most common and most likely answer to this crossword clue is the 6 letter word ASSERT
A
S
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E
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T
More clues leading to the result ASSERT
- Maintain a sizeable lock-up
- A sure thing, we hear, to declare
- Categorically declare a sure winner on radio?
- Declare a sure winner in speech
- State offers something worth having — it's right to join in
- Claim a foregone conclusion loudly
- Insist upon agreement with Republican for nomination in the first place
- A lock-up claim
- Insist upon actress performing without cocaine
- Swear in fool with bible, under arrest at last
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 = assert.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 ASSERT mean?
ASSERT noun- An assertion; a section of source code which tests whether an expected condition is true.
- To declare with assurance or plainly and strongly; to state positively.
- To use or exercise and thereby prove the existence of.
- To maintain or defend, as a cause or a claim, by words or measures; to vindicate a claim or title to
- To specify that a condition or expression is true at a certain point in the code.
- To set a signal on a line using a voltage or electric current.