Not in motion yet (5)
I believe the answer is:
'yet' is the definition.
(I know that yet can be written as still)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for still that I've seen before include "Even now; not moving" , "Motionless, not sparkling" , "Static photograph" , "It's not effervescing" , "gentle" .)