The line that's supporting you (6)
I believe the answer is:
career
'the line' is the definition.
(career is a kind of line)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for career that I've seen before include "go very fast" , "Whole of employment" , "Gallop" , "course securing professional employment" , "charge" .)