Permit is required to get into Virginia (4)
I believe the answer is:
visa
'permit' is the definition.
(I know that visa is a more specific form of the action O.K.)
'is required to get into virginia' is the wordplay.
I cannot really understand how this works, but
'is' is present in the answer.
'virginia' could be 'va' (US state abbreviation) and 'va' is found in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for visa that I've seen before include "Endorsement made in a passport" , "Authorisation to enter a country" , "travel authority" , "Travel pass" , "Travel stamp in passport" .)