Focal point (4)
'focal point' is the definition.
(hub can mean a centre or focal point)
This is the entire clue.
(Other definitions for hub that I've seen before include "Wheel's centre" , "Centre (of network)" , "Centre of activity" , "Centre of wheel" , "throbbing heart" .)
'focal 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 "branch perhaps at this point" , "part of network" , "Knot - swelling - knob" , "Where network lines meet" , "Natural swelling of part of a plant or animal" .)