The most common and most likely answer to this crossword clue is the 9 letter word INDUCTION
I've seen this crossword clue in The Times
I
N
D
U
C
T
I
O
N
Buddy explains!
The straight part
We know that "investiture" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case investiture = induction.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 INDUCTION mean?
INDUCTION noun- An act of inducting.
- An act of inducing.
- The process of inducing the birth process.
- An introduction.