Possible Clues:

• One is in the nostrils, by the sound of them
• Cat burglars' no-nos
• Sounds off, possibly, in the theatre
• On the face of them I get into them by the sound of them
• One is in snouts, by the sound of them
• Sound snouts surround a single
• One is in a snouty setting for them to be sound
• Snap, crackle and pop, e.g.
• One in them on the face of them by the sound of them
• Is 'e in the son of 5 downs?