The most common and most likely answer to this crossword clue is the 8 letter word DAMAGING
I've seen this crossword clue in The Daily Telegraph
D
A
M
A
G
I
N
G
Buddy explains!
The straight part
We know that "It’s certainly not helping" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s certainly not helping = damaging.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 DAMAGING mean?
DAMAGING verb- To impair the soundness, goodness, or value of; to harm or cause destruction.
- To undergo damage.
- An act of causing damage.
- Harmful; injurious; causing damage.