Mock downsized form of border identification (6)
I believe the answer is:
deride
'mock' is the definition.
(deriding is a kind of mocking)
'of border identification' is the wordplay.
'of' indicates a hidden word.
'DERIDE' is hidden within 'border identification'.
'downsized form' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for deride that I've seen before include "Jeer, belittle" , "Mock, scorn" , "Poke fun at" , "Disparage" , "Speak of with contempt" .)