Exercise time, then shower? (5)

I believe the answer is:

train

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

But I can't explain it at all! Could you help me understand?

(Other definitions for train that I've seen before include "Retinue; sequence" , "Line of carriages with a locomotive" , "Trailing material on dress" , "Locomotive and coaches" , "Trailing part of bridal dress" .)

I've seen this clue in The Telegraph.

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.