The most common and most likely answer to this crossword clue is the 7 letter word YTTRIUM
I've seen this crossword clue in Independent
Y
T
T
R
I
U
M
More clues leading to the result YTTRIUM
- Table item, last of lousy dry alcohol I swallowed
- Showing unusual maturity, but lacking a certain element
- Y-fronts of yuppies threaten to rip if unwisely manspread
- Hollow Yorkist victory without local element
- Dry recipe? I admitted, I love the food element
- Y-young teetotaller’s drink with setter
- Maturity perhaps lacking a natural element
- Rare element of maturity adult leaves out
Buddy explains!

The straight part
We know that "Y" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case y = yttrium.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 YTTRIUM mean?
YTTRIUM noun- A silvery metallic chemical element (symbol Y) with an atomic number of 39, mainly found in combination with lanthanide elements in rare-earth minerals.