The most common and most likely answer to this crossword clue is the 10 letter word CONTINUOUS
I've seen this crossword clue in The Times
C
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N
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The straight part
We know that "non-stop" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case non-stop = continuous.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.
Crossword Answer definitions
CONTINUOUS adjective- Without stopping; without a break, cessation, or interruption
- Without intervening space; continued
- Not deviating or varying from uniformity; not interrupted; not joined or articulated.
- (of a function) Such that, for every x in the domain, for each small open interval D about f(x), there's an interval containing x whose image is in D.
- (more generally, of a function between two topological spaces) Such that each open set in the target space has an open preimage (in the domain space, with respect to the given function).
- (grammar) Expressing an ongoing action or state.