The most common and most likely answer to this crossword clue is the 8 letter word DEMOLISH
I've seen this crossword clue in The Guardian
D
E
M
O
L
I
S
H
More clues leading to the result DEMOLISH
- Protest is about large harbour ruin
- Guzzle tasty sandwiches second
- Pull down pants seldom worn by current husband
- Tear down line in protest before I shut up
- Guzzle meal, including most of melon cocktail
- Protest by left is hard to refute completely
- Destroy shed — limo wrecked
- Ruin, perhaps as a march crushes Left
Buddy explains!

The straight part
We know that "Pull down" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pull down = demolish.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 DEMOLISH mean?
DEMOLISH verb- To destroy.
- To defeat or consume utterly (as a theory, belief or opponent).