Plants found in south facing borders (6)
I believe the answer is:
sedges
'plants' is the definition.
The answer is an example.
'south facing borders' is the wordplay.
'south' becomes 's' (synonyms).
'facing' says to put letters next to each other.
'borders' becomes 'edges' ('edge' can be a synonym of 'border').
's'+'edges'='SEDGES'
'found in' acts as a link.
(Other definitions for sedges that I've seen before include "Rush-like plants growing in wet places" , "Flies" .)