The most common and most likely answer to this crossword clue is the 8 letter word LAMBASTS
I've seen this crossword clue in The Times
L
A
M
B
A
S
T
S
More clues leading to the result LAMBASTS
Buddy explains!
The straight part
We know that "Assails" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case assails = lambasts.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 LAMBASTS mean?
LAMBASTS verb- To scold, reprimand or criticize harshly.
- (dated in UK English but not US English) To give a thrashing to; to beat severely.