The most common and most likely answer to this crossword clue is the 6 letter word FINING
I've seen this crossword clue in Financial Times
F
I
N
I
N
G
Buddy explains!
The straight part
We know that "punishing financially" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case punishing financially = fining.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 FINING mean?
FINING verb- To make finer, purer, or cleaner; to purify or clarify.
- To become finer, purer, or cleaner.
- To make finer, or less coarse, as in bulk, texture, etc.
- To change by fine gradations.
- To clarify (wine and beer) by filtration.
- To become gradually fine; to diminish; to dwindle (with away, down, or off).
- To issue a fine as punishment to (someone).
- To pay a fine.
- To finish; to cease.
- To cause to cease; to stop.