Possible Clues:

• Zip back on the river as an afterthought
• Rate at which sea ebbs towards sun
• 'More haste, less . . . . .'
• The going rate for an amphetamine
• Film sensitivity to light
• With children around, coppers get a move on!
• Sprinter's have it
• Word with bump or limit
• Obey the ___ limit
• Reeves thriller