The most common and most likely answer to this crossword clue is the 10 letter word SYNCOPATED
I've seen this crossword clue in The Times
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Buddy explains!

The straight part
We know that "a certain rhythm" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a certain rhythm = syncopated.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 SYNCOPATED mean?
SYNCOPATED verb- To omit a vocalic or consonantal sound or a syllable from a word; to use syncope
- To stress or accentuate the weak beat of a rhythm; to use syncopation
- (grammar) of a word, shortened by syncope
- Of a rhythm, modified by syncopation