The most common and most likely answer to this crossword clue is the 9 letter word ATTENUATE
I've seen this crossword clue in Independent
A
T
T
E
N
U
A
T
E
More clues leading to the result ATTENUATE
- They say solver had dinner late to lose strength
- To become thin you had a latish breakfast according to text?
- Ready for first shot when interrupted by idiot grabbing one? That’ll make you weaken
- Become thin — from what we hear, you dined late
- Slim down, getting neat and taut, exercising with energy
- Reduced time for news update after not getting paid
- When it's bedtime finally, you brew tea that's dilute
- Become less dense and almost go to university at Cambridge finally
Buddy explains!

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 ATTENUATE mean?
ATTENUATE verb- To reduce in size, force, value, amount, or degree.
- To make thinner, as by physically reshaping, starving, or decaying.
- To become thin or fine; to grow less.
- To weaken.
- To rarefy.
- To reduce the virulence of a bacterium or virus.
- To reduce the amplitude of an electrical, radio, or optical signal.
- (of a beer) To become less dense as a result of the conversion of sugar to alcohol.
- (of leaves) Gradually tapering into a petiole-like extension toward the base.