The most common and most likely answer to this crossword clue is the 9 letter word BEGINNING
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More clues leading to the result BEGINNING
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 = beginning.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 BEGINNING mean?
BEGINNING noun- The act of doing that which begins anything; commencement of an action, state, or space of time; entrance into being or upon a course; the first act, effort, or state of a succession of acts or states.
- That which is begun; a rudiment or element.
- That which begins or originates something; the source or first cause.
- The initial portion of some extended thing.
- To start, to initiate or take the first step into something.
- To be in the first stage of some situation
- To come into existence.
- Of or relating to the first portion of some extended thing.