Prompt access to summit, often (4)
I believe the answer is:
'prompt' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for spur that I've seen before include "Lateral root" , "This provokes sudden movement!" , "Impetus" , "Inducement" , "Cowboy boot attachment" .)