The most common and most likely answer to this crossword clue is the 7 letter word LONGISH
I've seen this crossword clue in The Daily Telegraph
L
O
N
G
I
S
H
More clues leading to the result LONGISH
Buddy explains!
The straight part
We know that "extended, to an extent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case extended, to an extent = longish.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 LONGISH mean?
LONGISH adjective- Somewhat long.