The most common and most likely answer to this crossword clue is the 7 letter word PANTHER
I've seen this crossword clue in Financial Times
P
A
N
T
H
E
R
More clues leading to the result PANTHER
- Leopard one breathless catching horse?
- Knight blocking way in front of Her Majesty is just a big pussycat
- Prowler, male part on parade, initially
- Gasp — that woman not suitable for 1 across
- Cat woman’s after singular underwear
- One longing apparently to take in first sign of Himalayan wild cat
- Spotted feline quietly sitting on part of plant
- Run down the king’s cat
- Cat and part of flower shown on page
- Animal trail encompassing northern outskirts of Ecuador
Buddy explains!

The straight part
We know that "a big pussycat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a big pussycat = panther.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 PANTHER mean?
PANTHER noun- Any of various big cats with black fur; most especially, the black-coated leopard of India.
- Any big cat of the genus Panthera.
- A cougar; especially the Florida panther.
- A creature resembling a big cat with a multicolored hide, found in Ancient Greek mythology.