The most common and most likely answer to this crossword clue is the 5 plus 1 plus 7 plus 2 plus 3 plus 5 letter word THROW A SPANNER IN THE WORKS
I've seen this crossword clue in The Times
T
H
R
O
W
A
S
P
A
N
N
E
R
I
N
T
H
E
W
O
R
K
S
More clues leading to the result THROW A SPANNER IN THE WORKS
Buddy explains!

The straight part
We know that "block progress" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case block progress = throw a spanner in the works.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.