The most common and most likely answer to this crossword clue is the 8 letter word DOORSTOP
I've seen this crossword clue in The Daily Telegraph
D
O
O
R
S
T
O
P
Buddy explains!
The straight part
We know that "Block" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case block = doorstop.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 DOORSTOP mean?
DOORSTOP noun- Any device or object used to halt the motion of a door, as a large or heavy object, a wedge, or some piece of hardware fixed to the floor, door or wall.
- A large book, which by implication could be used to stop a door.
- (in error for doorstep) A thick sandwich.
- An interview with a politician or other public figure (apparently informal or spontaneous but often planned), as they enter or leave a building.