Landed gentry secure border
I believe the answer is:
edge
'border' is the definition.
(synonyms)
'landed gentry secure' is the wordplay.
'secure' indicates a hidden word (I've seen 'securing' mean this).
'EDGE' is hidden in the letters of 'landed gentry'.
(Other definitions for edge that I've seen before include "Brim" , "Border - meeting place" , "Demarcation" , "Rim - move gradually" , "Advantage (informal)" .)