Frontier without British arrangement (5)
I believe the answer is:
order
'arrangement' is the definition.
(order is a kind of arrangement)
'frontier without british' is the wordplay.
'frontier' becomes 'border' (I've seen this before).
'without' suggests deleting specific letters.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'border' with 'b' taken out is 'ORDER'.
(Other definitions for order that I've seen before include "Command; social class" , "American helping" , "Instruct" , "association" , "Command or written direction" .)