Possible Clues:

• Render purer
• Remove impurities from (eg, metals)
• Make one pay a second time to make one pure
• Fishing equipment endlessly contains part of fish to process
• It will make it more pure to have it on the swimmer in the lough
• Make one pay a second time? That'll make one purer
• Remove impurities or make cultured
• Filter or process as with oil
• Purify or improve
• Purify or make more cultured