The most common and most likely answer to this crossword clue is the 9 letter word INSTIGATE
I've seen this crossword clue in The Times
I
N
S
T
I
G
A
T
E
More clues leading to the result INSTIGATE
- Found popular part of US to house retired soldier
- Start hesitating hopelessly after husband leaves
- Bring about a sit-in – get organised
- Start eating, it’s fantastic!
- Launch isn’t off: one opening
- Prompt to redevelop giant site
- Start teasing it out
- To start off, it’s roughly covered by home attendance
- Prompt soldier’s going west, getting aboard in Washington, say
- Giant set free bears I provoke
Buddy explains!

The straight part
We know that "Start" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case start = instigate.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 INSTIGATE mean?
INSTIGATE verb- To incite; to bring about by urging or encouraging
- To goad or urge (a person) forward, especially to wicked actions; to provoke