The most common and most likely answer to this crossword clue is the 4 letter word UREA
I've seen this crossword clue in Independent
U
R
E
A
More clues leading to the result UREA
- Office uncovered waste product
- Waste product from bureau
- Federal investigators over the pond uncovered something in the water
- Compound rate’s void in Ukraine
- Top-class gunmen conserve energy but waste material
- Number one ingredient in office lacking boundaries
- Flower given a bit of water?
- Secretion from impure animal
- River of top quality? It’s in the water
- Waste product from bureaucracy
Buddy explains!
The straight part
We know that "Number one ingredient" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case number one ingredient = urea.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 UREA mean?
UREA noun- A water-soluble organic compound, CO(NH2)2, formed by the metabolism of proteins and excreted in the urine.
- Any N-substituted derivative of urea, with the general formula (R1R2N)CO(NR3R4).