Possible Clues:

• Mound built by a colony
• Insect's home
• The nth one in the works is a home for a 21-down
• Everyone swallows obscure hint the queen's home
• Built-up colony is unable to freeze when cold is completely kept out
• Many a worker here right to avoid an exciting experience
• Insect colony
• Built by the workers for relative heard in Croke Park
• Home for social workers?
• Mound of earth formed by insects digging their underground nest