The most common and most likely answer to this crossword clue is the 8 letter word BROADEST
I've seen this crossword clue in The Guardian
B
R
O
A
D
E
S
T
Buddy explains!
The straight part
We know that "widest" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case widest = broadest.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 BROADEST mean?
BROADEST adjective- Wide in extent or scope.
- Extended, in the sense of diffused; open; clear; full.
- Having a large measure of any thing or quality; unlimited; unrestrained.
- Comprehensive; liberal; enlarged.
- Plain; evident.
- (writing) Unsubtle; obvious.
- Free; unrestrained; unconfined.
- Gross; coarse; indelicate.
- (of an accent) Strongly regional.
- (Gaelic languages) Velarized, i.e. not palatalized.