Permit everyone to know finally (5)
I believe the answer is:
allow
'permit' is the definition.
('allow' can be a synonym of 'permit')
'everyone to know finally' is the wordplay.
'everyone' becomes 'all' (I've seen this before).
'finally' suggests the final letters.
The last letters of 'to know' are 'ow'.
'all'+'ow'='ALLOW'
(Other definitions for allow that I've seen before include "Permit or concede" , "Give leave to" , "Permit, let happen" , "OK" , "Sanction" .)