Demands for British to leave frontiers (6)
I believe the answer is:
orders
'demands' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for orders that I've seen before include "'Instructions, commands (6)'" , "Decrees, commands" , "Given to soldiers" , "Dictates, commands" , "Groups living under particular religious rules" .)