Scrabble has four of these things rambler may need to negotiate (6)
I believe the answer is:
stiles
'things rambler may need to negotiate' is the definition.
(stiles are gates a rambler might climb over)
I can't explain the rest of the clue.
(Other definitions for stiles that I've seen before include "Sets of steps in fences" , "Steps to help walkers over fences or walls" , "Sets of steps in a fence" , "Fence-steps in islets" .)