Possible Clues:

• Gets one fit to be on-line
• Prepares to run a marathon, say
• That makes one fit for 30 across
• Coaches time run - and it never stops the leaders
• Makes one fit for when it's wet after tea
• That makes them fit to go by rail
• This makes one fit to go by rail
• Locomotive-drawn rail cars
• Track group?
• Expresses, maybe