Everyone understands the danger is past (3,5)
I believe the answer is:
'the danger is past' is the definition.
(I've seen this before)
'everyone understands' is the wordplay.
'everyone' becomes 'all' (all people).
'understands' becomes 'clear' (I am not sure about this - if you are sure you should believe this answer much more).
Can you help me to learn more?
(Other definitions for all clear that I've seen before include "Understood" , "Signal danger is ended" , "Siren sound to mark end of bombing by planes" , "no doubts" , "Message confirming safety" .)