The most common and most likely answer to this crossword clue is the 8 letter word ETERNITY
I've seen this crossword clue in The Daily Telegraph
E
T
E
R
N
I
T
Y
More clues leading to the result ETERNITY
- Tiny tree, gnarled for yonks
- Without Conservatives city centre declined seemingly forever
- Change in entirety, for all time
- Aquatic bird — it nested in banks of estuary for donkey's years
- Tiny tree struggling for a very long time
- Tiny tree flowering forever
- Teen I try to reform for a long time!
- A very long time to make a ring
- Time in entirety, perhaps
- Bird that’s coming back round initially thanks you forever
Buddy explains!

The straight part
We know that "You never come to the end of this sort of ring" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case you never come to the end of this sort of ring = eternity.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 ETERNITY mean?
ETERNITY noun- Existence without end, infinite time.
- Existence outside of time.
- A period of time which extends infinitely far into the future.
- (metaphysical) The remainder of time that elapses after death.
- A comparatively long time.