The most common and most likely answer to this crossword clue is the 8 letter word HEAVIEST
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result HEAVIEST
Buddy explains!
The straight part
We know that "most weighty" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case most weighty = heaviest.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 HEAVIEST mean?
HEAVIEST adjective- (of a physical object) Having great weight.
- (of a topic) Serious, somber.
- Not easy to bear; burdensome; oppressive.
- Good.
- (late 1960s, 1970s) Profound.
- (of a rate of flow) High, great.
- Armed.
- Louder, more distorted.
- (of weather) Hot and humid.
- (of a person) Doing the specified activity more intensely than most other people.
- (of food) High in fat or protein; difficult to digest.
- Of great force, power, or intensity; deep or intense.
- Laden to a great extent.
- Laden with that which is weighty; encumbered; burdened; bowed down, either with an actual burden, or with grief, pain, disappointment, etc.
- Slow; sluggish; inactive; or lifeless, dull, inanimate, stupid.
- Impeding motion; cloggy; clayey.
- Not raised or leavened.
- (of wines or spirits) Having much body or strength.
- With child; pregnant.
- Containing one or more isotopes that are heavier than the normal one
- (petroleum) with high viscosity