The most common and most likely answer to this crossword clue is the 5 plus 2 letter word SPEED UP
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Buddy explains!

The straight part
We know that "Go faster" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case go faster = speed 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 SPEED UP mean?
SPEED UP noun- An amount or rate of decrease in time taken to do a certain amount of work.
- The relationship between time taken and number of processors used.
- (labor) An employer's demand for more output without more pay.