Ascend, mount (5)
I believe the answer is:
climb
I believe this is a double definition.
'ascend' is the first definition.
(climbing is a kind of ascending)
'mount' is the second definition.
(I know that mount can be written as climb)
(Other definitions for climb that I've seen before include "Go higher up" , "Go up - scale" , "Ascend, scale" , "Use hands and feet to rise" , "showing the way up" .)