The most common and most likely answer to this crossword clue is the 10 letter word ANACOLUTHA
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The straight part
We know that "ungrammatical constructions" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ungrammatical constructions = anacolutha.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 ANACOLUTHA mean?
ANACOLUTHA noun- (grammar) A sentence or clause that is grammatically inconsistent, especially with respect to the type of clausal or phrasal complement for the initial clause.
- Intentional use of such a structure.