70 aides get exposed late in the day (8)
I believe the answer is:
eventide
'late in the day' is the definition.
(I've seen this before)
'70 aides get exposed' is the wordplay.
'70' becomes 'event' (I am not sure about this - if you are sure you should believe this answer much more).
'get exposed' indicates the central letters (inside letters are exposed without outside ones).
The centre of 'aides' is 'ide'.
'event'+'ide'='EVENTIDE'
(Other definitions for eventide that I've seen before include "The day's close (poetic)" , "sunset" , "End of the day (poetic)" , "late in the day?" , "onset of dusk" .)