Right to proceed with regard to eliminating duplication (4)
I believe the answer is:
visa
'right' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for visa that I've seen before include "Travel stamp in passport" , "Mark on passport" , "Travel document is required to enter Virginia" , "Passport stamp or well-known credit card" , "Stamp affixed to passport as permission to enter country" .)