The most common and most likely answer to this crossword clue is the 5 letter word VOMIT
I've seen this crossword clue in The Guardian
V
O
M
I
T
Buddy explains!
The straight part
We know that "cat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cat = vomit.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 VOMIT mean?
VOMIT noun- The regurgitated former contents of a stomach; vomitus.
- The act of regurgitating.
- That which causes vomiting; an emetic.
- To regurgitate or eject the contents of the stomach through the mouth; puke.
- To regurgitate and discharge (something swallowed); to spew.
- To eject from any hollow place; to belch forth; to emit.