The most common and most likely answer to this crossword clue is the 10 letter word INADEQUATE
I've seen this crossword clue in The Daily Telegraph
I
N
A
D
E
Q
U
A
T
E
More clues leading to the result INADEQUATE
Buddy explains!

The straight part
We know that "Wanting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case wanting = inadequate.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 INADEQUATE mean?
INADEQUATE noun- An individual who is inadequate.
- Not adequate; not fit for the purpose