Plant from south facing border (5)
I believe the answer is:
sedge
'plant' is the definition.
The answer is an example.
'south facing border' is the wordplay.
'south' becomes 's' ('S' can be a synonym of 'south').
'facing' means one lot of letters go next to another.
'border' becomes 'edge' ('edge' can be a synonym of 'border').
's'+'edge'='SEDGE'
'from' is the link.
(Other definitions for sedge that I've seen before include "Marsh grass" , "Grass-like plant growing in marshes" , "Coarse grassy plant" , "plant with triangular stems" , "fly by rivers" .)