Second piece of open country gets protection (6)
I believe the answer is:
sheath
'protection' is the definition.
(sheath is a kind of protection)
'second piece of open country' is the wordplay.
'second' becomes 's' (common abbreviation).
'piece of open country' becomes 'heath'.
's'+'heath'='SHEATH'
'gets' acts as a link.
(Other definitions for sheath that I've seen before include "Close fitting dress" , "Case for a dagger" , "Sword covering" , "Scabbard" , "Cover for a sword" .)