The most common and most likely answer to this crossword clue is the 5 plus 2 letter word START UP
I've seen this crossword clue in The Guardian
S
T
A
R
T
U
P
More clues leading to the result START UP
- Begin with famous sheep
- Set in motion by leading sheep
- Place singers from the east get going
- Fledgling company to rise suddenly
- Establish Italian restaurants?
- Found drink to be laced with acid
- Get going from place with vermin running round
- Begin drink, downing bitter
- Get going with celebrity goat
- Begin feast, consuming pie
Buddy explains!

The straight part
We know that "Begin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case begin = start up.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 START UP mean?
START UP noun- The act or process of starting a process or machine.
- A new company or organization or business venture designed for rapid growth.