The most common and most likely answer to this crossword clue is the 12 letter word TRANSGRESSED
I've seen this crossword clue in The Times
T
R
A
N
S
G
R
E
S
S
E
D
More clues leading to the result TRANSGRESSED
Buddy explains!

The straight part
We know that "offended" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case offended = transgressed.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 TRANSGRESSED mean?
TRANSGRESSED verb- To exceed or overstep some limit or boundary.
- To act in violation of some law.
- (construed with against) To commit an offense; to sin.
- (of the sea) To spread over land along a shoreline; to inundate.