The most common and most likely answer to this crossword clue is the 7 letter word ASSAULT
I've seen this crossword clue in The Sunday Telegraph
A
S
S
A
U
L
T
More clues leading to the result ASSAULT
- A saint will protect Biblical leader in onslaught
- Attack a sailor, by the sound of it
- A way to catch old king in raid
- Attack a sailor by the sound of it
- Attack an old sailor picked up by the ears?
- A matelot, reportedly offensive
- A sailor caught in storm
- Attack a sailor verbally
- Reportedly, a sailor can be offensive
- Attack fool not beginning to jump
Buddy explains!

The straight part
We know that "Offensive" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case offensive = assault.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 ASSAULT mean?
ASSAULT noun- A violent onset or attack with physical means, for example blows, weapons, etc.
- A violent onset or attack with moral weapons, for example words, arguments, appeals, and the like
- An attempt to commit battery: a violent attempt, or willful effort with force or violence, to do hurt to another, but without necessarily touching his person, as by lifting a fist in a threatening manner, or by striking at him and missing him.
- The crime whose action is such an attempt.
- An act that causes someone to apprehend imminent bodily harm.
- The tort whose action is such an act.
- A non-competitive combat between two fencers.
- To attack, physically or figuratively.
- To threaten or harass.