The most common and most likely answer to this crossword clue is the 9 letter word RECONVICT
I've seen this crossword clue in The Guardian
R
E
C
O
N
V
I
C
T
More clues leading to the result RECONVICT
Buddy explains!

The straight part
We know that "Repeat sentence" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case repeat sentence = reconvict.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 RECONVICT mean?
RECONVICT verb- To convict again