Follow the line (5)
I believe the answer is:
track
I believe this clue is a double definition.
'follow' is the first definition.
(I know that track is a more specific form of follow)
'line' is the second definition.
(track is a kind of line)
'the' is the link.
(Other definitions for track that I've seen before include "A prepared course for racing on" , "Trace; path" , "One song on CD?" , "One of the songs on CD?" , "Lines" .)