The most common and most likely answer to this crossword clue is the 6 plus 5 letter word MOBIUS STRIP
I've seen this crossword clue in The Guardian
M
O
B
I
U
S
S
T
R
I
P
More clues leading to the result MOBIUS STRIP
Buddy explains!
The straight part
We know that "seemingly no end to it? /seemingly no end to it?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case seemingly no end to it? /seemingly no end to it? = mobius strip.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.