The most common and most likely answer to this crossword clue is the 9 letter word OVEREATEN
I've seen this crossword clue in The Guardian
O
V
E
R
E
A
T
E
N
Buddy explains!

The straight part
We know that "polished off too much" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case polished off too much = overeaten.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 OVEREATEN mean?
OVEREATEN verb- To eat too much.
- To surfeit with eating.