Possible Clues:

• How the centre might dig for the defence with HC?
• Establish firmly in well-defended position
• Dispatched Parisians (having twice surrendered capital) to dig in
• Establish oneself in French river with fish going round
• Very firmly establish
• Implant
• Establish a person with authority to break up currency going to Switzerland
• Dig for defence to fix it firmly
• Establish space by river and fish around
• Dig in unusual tree in front of new church with name inscribed