The most common and most likely answer to this crossword clue is the 11 letter word ENLARGEMENT
I've seen this crossword clue in The Guardian
E
N
L
A
R
G
E
M
E
N
T
More clues leading to the result ENLARGEMENT
Buddy explains!
The straight part
We know that "Stretching" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stretching = enlargement.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 ENLARGEMENT mean?
ENLARGEMENT noun- The act of making something larger.
- A making more obvious or serious; exacerbation.
- An image, particularly a photograph, that has been enlarged.
- Freedom from confinement; liberty.
- Diffuseness of speech or writing; a speaking at length.