Parts of the foot (6)
I believe the answer is:
inches
'parts of the foot' is the definition.
The answer and definition can be both to do with motion as well as being verbs in their -s form.
Maybe there's an association between them I don't understand?
This is the entire clue.
Can you help me to learn more?
(Other definitions for inches that I've seen before include "Islands; measurements" , "Scottish islands" , "Edges slowly" , "Twelves of these in a foot" , "Moves away; units of measurement" .)