The most common and most likely answer to this crossword clue is the 4 plus 4 letter word SLOW DOWN
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More clues leading to the result SLOW DOWN
Buddy explains!
The straight part
We know that "lose speed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lose speed = slow down.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 SLOW DOWN mean?
SLOW DOWN noun- A reduction in speed, or a decrease in the level of production, etc.