The most common and most likely answer to this crossword clue is the 8 letter word IMPEDING
I
M
P
E
D
I
N
G
Buddy explains!

The straight part
We know that "obstructing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case obstructing = impeding.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 IMPEDING mean?
IMPEDING verb- To get in the way of; to hinder.