Poles ordered to protect a border city (2,4)
I believe the answer is:
el paso
'border city' is the definition.
(I've seen this in another clue)
'poles ordered to protect a' is the wordplay.
'ordered' indicates an anagram.
'to protect' means one lot of letters goes inside another.
'poles' with letters rearranged gives 'elpso'.
'elpso' placed around 'a' is 'EL PASO'.
(Other definitions for el paso that I've seen before include "City of Texas on the Rio Grande; aslope (anag.)" , "Texan city" , "city on Mexican border" , "US city" , "West Texas town" .)