The most common and most likely answer to this crossword clue is the 10 letter word FREEWHEELS
I've seen this crossword clue in Financial Times
F
R
E
E
W
H
E
E
L
S
Buddy explains!
The straight part
We know that "coasts" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case coasts = freewheels.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 FREEWHEELS mean?
FREEWHEELS noun- A device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft.