The most common and most likely answer to this crossword clue is the 10 letter word POSSESSING
I've seen this crossword clue in The Daily Telegraph
P
O
S
S
E
S
S
I
N
G
Buddy explains!
The straight part
We know that "Having" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case having = possessing.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 POSSESSING mean?
POSSESSING verb- To have; to have ownership of.
- To take control of someone's body or mind, especially in a supernatural manner.
- (chiefly with of) To vest ownership in (someone, or oneself); to give someone power or knowledge; to acquaint; to inform.