The most common and most likely answer to this crossword clue is the 5 letter word TABBY
I've seen this crossword clue in The Daily Telegraph
T
A
B
B
Y
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 = tabby.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 TABBY mean?
TABBY noun- A kind of waved silk, usually called watered silk, manufactured like taffeta, but thicker and stronger. The watering is given to it by calendering.
- A mixture of lime with shells, gravel, or stones, in equal proportions, with an equal proportion of water. When dry, this becomes as hard as rock.
- A brindled cat.
- An old maid or gossip.
- To give a wavy or watered appearance to (a textile).
- Having a wavy or watered appearance
- Brindled; diversified in color