The most common and most likely answer to this crossword clue is the 5 letter word PUMAS
I've seen this crossword clue in The Times
P
U
M
A
S
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The straight part
We know that "Big felines" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case big felines = pumas.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 PUMAS mean?
PUMAS noun- The mountain lion or cougar, Puma concolor.
- A woman in her 20s or 30s who seeks relationships with younger men; a younger cougar.