Possible Clues:

• Old boy on solitary trail is on the way out
• Getting dated, old boy only put on perfume
• Relaid cobblestones avoided by British as going out of fashion
• Former pupil's only trace is out of date
• Pupil who's left single trace on the way out
• One nose visible under ex-pupil's old hat
• Becoming out of date
• Initially offended by smell of fish past its sell-by date?
• On the way out
• Wobbly cobblestones bishop avoided on the way out