The most common and most likely answer to this crossword clue is the 7 letter word CASCARA
I've seen this crossword clue in The Guardian
C
A
S
C
A
R
A
Buddy explains!

The straight part
We know that "a means of restoring motion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a means of restoring motion = cascara.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 CASCARA mean?
CASCARA noun- A North American buckthorn (Frangula purshiana, syn. Rhamnus purshiana) whose bark is used as a laxative.
- Dried coffee cherry fruit used in teas and other drinks.