The most common and most likely answer to this crossword clue is the 8 letter word FELONIES
I've seen this crossword clue in The Guardian
F
E
L
O
N
I
E
S
More clues leading to the result FELONIES
Buddy explains!

The straight part
We know that "Offences" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case offences = felonies.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 FELONIES mean?
FELONIES noun- A serious criminal offense, which, under United States federal law, is punishable by imprisonment for a term exceeding one year or by death.