Possible Clues:

• Anatomical cavity
• Social worker given drink in chamber
• Cavity in a body organ
• By the sound of it, one knows where to find it - but not in Ulster, by the sound of it (6)r
• Cavity within a bone, like sinus in upper jaw
• The drink for the insect gets up its nose
• This may lead one to Ulster, by the sound of it, by the nose
• Chamber with drink approached by worker
• Sound in the North in the nose
• Cavity within a bone, like a sinus