The most common and most likely answer to this crossword clue is the 8 letter word BLACKING
I've seen this crossword clue in Financial Times
B
L
A
C
K
I
N
G
More clues leading to the result BLACKING
Buddy explains!
The straight part
We know that "Polish" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case polish = blacking.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 BLACKING mean?
BLACKING verb- To make black; to blacken.
- To apply blacking to (something).
- To boycott, usually as part of an industrial dispute.
- A preparation, containing lampblack, used to produce a shiny black coating.
- Shoe polish.