The most common and most likely answer to this crossword clue is the 12 letter word IMPERISHABLE
I've seen this crossword clue in The Daily Telegraph
I
M
P
E
R
I
S
H
A
B
L
E
More clues leading to the result IMPERISHABLE
Buddy explains!

The straight part
We know that "Enduring" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case enduring = imperishable.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 IMPERISHABLE mean?
IMPERISHABLE noun- (in the plural) something that does not perish, or keeps for a long time
- Not perishable; not subject to decay; enduring permanently