Possible Clues:

• What sounds like region down below barrier
• Anti-erosion breakwater
• The genitals, we hear, of a mole?
• Barrier built on beach
• Curved edge in the auditorium's barrier
• Teeny organisation's infiltrated by opposing mole
• Beach-protecting wall
• Wild eryngo where there's a breakwater
• Erosion-control wall
• It's built as an ocean container