Possible Clues:

• Main, as a highway
• Main channel's receiver concealing coating of rust
• Antenna limits radio telephony along major roads
• A new trailer on an important route?
• Relating to major routes
• Like major thoroughfare in which a trailer gets wrecked
• Driven on frequently
• Hesitation in a complex trial of major routes
• Road descriptor
• Like a main channel, a channel in a font