Possible Clues:

• Go faster, with "it"
• Walk into a train car
• Pesto, crackers and centre of squash, in a way
• Squash, perhaps
• Press, as an accelerator
• Squash like a bug
• Suppress encouragement to speed -- it isn't necessary
• "Don't ___ the Grass, Sam"
• Put underfoot
• Activate, as a wah-wah pedal