Possible Clues:

• Call for final letters of the Forces
• Most recent appointment gets the call
• Evening collection for mourning people?
• 'No more letters at the end of the day, by the sound of it (4,4)'
• The final sound of no more letters after this
• Call from the army missed by tardy correspondent
• Situation after most recent call for retirement
• What may be trumpeted as the ultimate appointment
• Continue with letters, passing notes from the military?
• It's played at bedtime in the army