The most common and most likely answer to this crossword clue is the 6 letter word NARKED
I've seen this crossword clue in The Daily Telegraph
N
A
R
K
E
D
More clues leading to the result NARKED
- Cross Noah initially put in his boat?
- Newton and Drake, sadly, were annoying
- Annoyed the Queen comes in wearing nothing
- Annoyed by Rex entering without the usual protection
- Kelly replacing Noah, having his nose put out of joint
- Angry Republican enters undisguised
- Irritated king with bare exterior
- Ratty‘s boat kept in hideaway capsized
- Annoyed by overt resistance inside
- Open, reserving right to be annoyed
Buddy explains!

The straight part
We know that "Ratty" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ratty = narked.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 NARKED mean?
NARKED verb- To watch; to observe.
- To serve or behave as a spy or informer.
- To annoy or irritate.
- To complain.
- (often imperative) To stop.