Possible Clues:

• Powerful tractor for clearing ground
• Earth-moving machine
• Earth mover
• Beast that's 13 is a pushy one
• Noisy earth-moving machine
• At the end of the Archers, person dropping off heavy tractor
• Droll zebu's capering - it makes the earth move
• One pushes half a tree trunk on lines supported by sleeper
• Clearer message from Pope: achieve nothing without love
• Although he's apparently beastly sleepy, is very pushful