The most common and most likely answer to this crossword clue is the 4 plus 3 letter word DEAD END
I've seen this crossword clue in The Daily Telegraph
D
E
A
D
E
N
D
More clues leading to the result DEAD END
- Precise purpose, but no prospect of progress here
- Demanded changes after Mike leaves cul-de-sac
- Complete before the last part in which further progress is impossible
- A hideout in semi-wooded cul-de-sac
- Very close to stalemate
- Seeing late goal, one’s going nowhere
- Late finish? There’s no way out of it
- Late goal that leads nowhere
- Half-hearted action about a study that’s leading nowhere
- Hopeless situation somehow saddened society missing out
Buddy explains!

The straight part
We know that "blind alley" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case blind alley = dead end.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.
Crossword Answer definitions
DEAD END noun- A road with no exit.
- (by extension) A position that offers no hope of progress.
- To come to a dead-end.
- Going nowhere; blocked.