Junction point (4)
I believe the answer is:
node
'junction point' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for node that I've seen before include "Lump at junction" , "Thickened enlargement" , "Swelling - point of junction" , "Natural swelling of part of a plant or animal" , "branch perhaps at this point" .)