Meet prisoner on border (8)
I believe the answer is:
converge
'meet' is the definition.
(I know that meet can be written as converge)
'prisoner on border' is the wordplay.
'prisoner' becomes 'con' (abbreviation for 'convict').
'on' means one lot of letters go next to another.
'border' becomes 'verge' (verging is a kind of bordering).
'con'+'verge'='CONVERGE'
(Other definitions for converge that I've seen before include "Tend towards a common point" , "tend to get together" , "Come towards the same point like Congreve" , "Come together" , "Move toward the same point" .)