Fence? Cross-country runner needs new start (7)

I believe the answer is:

barrier

I'm a little stuck... Click here to teach me more about this clue!

'fence?' is the definition.
(fence is a kind of barrier)

I can't explain the rest of the clue.

(Other definitions for barrier that I've seen before include "bar" , "Fence; obstacle" , "Obstacle to movement" , "Eg, fence" , "Rear rib creating an obstacle" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.