Is after you?
I believe the answer is:
are
'is after you?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for are that I've seen before include "Is, in the plural" , "live" , "(We/you/they) exist" , "Unit of land measure equal to 100 square metres" , "is for more than one" .)