Latest possible moment for silently remembering the Armistice? (8,4)
I believe the answer is:
eleventh hour
'latest possible moment' is the definition.
(the last chance to do something)
I can't explain the rest of the clue.
(Other definitions for eleventh hour that I've seen before include "a sixty-minute period" , "Latest possible moment" , "Last-minute" , "well before noon" , "Very last moment" .)