Related Clues:

• E.g. Livingstone with border to explore
• Sprinkle with flour
• Sharpness shown by doctor -- one deals with a lot of rubbish
• River-bed clearer
• Dig out mud (from a river, harbour, etc)
• Clear a channel
• Clear the bottom of a river
• Underwater excavator
• Clear, as a channel
• Scalloping apparatus
• Deepen, as a channel
• Become more acute
• Clean out a bed
• Clear (riverbed)
• Revolutionary director heading, for example, back to do some work down the Shannon