With regard to two travel documents, the last is incomplete
I believe the answer is:
vis-a-vis
'with regard to' is the definition.
(I've seen this before)
'two travel documents the last is incomplete' is the wordplay.
I cannot quite see how this works, but
'is' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for vis-a-vis that I've seen before include "With regard to" , "Face-to-face" , "In relation to, as compared with" , "Facing; in relation to" .)