The most common and most likely answer to this crossword clue is the 7 letter word DENTURE
I've seen this crossword clue in The Guardian
D
E
N
T
U
R
E
More clues leading to the result DENTURE
Buddy explains!

The straight part
We know that "Replacement chopper" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case replacement chopper = denture.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 DENTURE mean?
DENTURE noun- A set of teeth, the teeth viewed as a unit
- An artificial replacement of one or more teeth
- (often in the plural) a complete replacement of all teeth in a mouth