The most common and most likely answer to this crossword clue is the 10 letter word MOLYBDENUM
I've seen this crossword clue in The Guardian
M
O
L
Y
B
D
E
N
U
M
More clues leading to the result MOLYBDENUM
Buddy explains!
The straight part
We know that "Mo" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mo = molybdenum.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 MOLYBDENUM mean?
MOLYBDENUM noun- A chemical element (symbol Mo) with an atomic number of 42: a silvery metal, not found as a free element, used in steel alloys.
- A single atom of this element.