Cautiously moving border (6)
I believe the answer is:
This clue could be a double definition.
'cautiously moving' is the first definition.
The answer and definition can be both to do with motion as well as being present participle verbs.
Maybe you can see an association between them that I can't see?
'border' is the second definition.
(I know that edging is a type of border)
Can you help me to learn more?
(Other definitions for edging that I've seen before include "Moving slowly sideways" , "Inching sideways" , "Making a border" , "Siding; border" , "Advancing slowly on the fringing?" .)