*Chain of hills (6)
'chain of hills' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ridge that I've seen before include "Line of raised ground" , "Escarpment" , "Hog's back" , "drum" , "Bump between furrows" .)
(Other definitions for bridge that I've seen before include "Span of popular card game" , "Span, connecting structure" , "Where four hands are needed" , "British composer" , "Captain's area on a ship" .)