Ride with team travelling the Circle Line (8)
I believe the answer is:
diameter
'circle line' is the definition.
(I've seen this in another clue)
'ride with team travelling' is the wordplay.
'with' says to put letters next to each other.
'travelling' indicates anagramming the letters.
'ride' after 'team' is 'teamride'.
'teamride' with letters rearranged gives 'DIAMETER'.
'the' is the link.
(Other definitions for diameter that I've seen before include "width of bar" , "Line connecting the centre of a circle with two points on the perimeter" , "Longest chord of a circle" , "Line crossing centre of sphere" , "Remade it to width of a circle" .)