The most common and most likely answer to this crossword clue is the 10 letter word DISPERSANT
I've seen this crossword clue in The Times
D
I
S
P
E
R
S
A
N
T
Buddy explains!
The straight part
We know that "It spreads" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it spreads = dispersant.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 DISPERSANT mean?
DISPERSANT noun- Any substance that is used to prevent settling or clumping of particles suspended in a liquid.