The most common and most likely answer to this crossword clue is the 7 letter word AGELESS
I've seen this crossword clue in Financial Times
A
G
E
L
E
S
S
More clues leading to the result AGELESS
- Perennial idiot without setter’s energy
- Eternal fool to accept point by setter?
- Eternal princess’s elegance resurrected in part
- Perennial to grow up the French windows at rear
- Some silica gel essence makes you eternally young
- Eternal message of some wrinkle-defying products?
- Enduring wobbly sea-legs
- Worthless stu?, this? It’s garb that never dates
- Eternal promise of face-cream factors?
- Forever youthful wrinkly gal, see, heading for Scotch
Buddy explains!

The straight part
We know that "Eternal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case eternal = ageless.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 AGELESS mean?
AGELESS adjective- (relative to past) Having existed for so great a period of time that its longevity cannot be expressed.
- (relative to future) Continuing infinitely or indefinitely.
- Always appearing youthful; never seeming to age.